Marvel's X-Men have provided us with a lot of big, world-defining moments throughout their history. Yes, some have actually managed to live up to the oft-hyped billing, changing the status quo of things. While a few hit the mark, many have missed, but what's undeniable is that they have provided us with a lot of controversy and talking points over the years. The movies from Fox have been polarizing but when added to the twists and turns in the comics, you can see why the children of the atom are just as hot a property as the Avengers, no matter the medium.

RELATED: The 15 Worst Episodes Of X-Men: The Animated Series

Mutants will always be under the microscope because of how intriguing they are, whether they're being led by Professor Xavier, Cyclops, Emma Frost, Wolverine or Magneto. They are considered outsiders and even after integrating into books like Avengers Arena and Uncanny Avengers, you can't help but feel they'll always be on the fringes. Even recently in Secret Empire, you can see that mutantkind has and will always be a huge part of big crossovers and storylines. So, with that in mind, CBR decided to look into some of the most controversial arcs, plots and overall events involving the species to this very day.

SPOILER WARNING: Spoilers ahead for several X-Men comics and events!

15 SCHISM: THE MUTANT CIVIL WAR

Wolverine and Cyclops fighting over the Schism

After seeing the Avengers torn apart in Mark Millar's Civil War event, Marvel decided to give the same treatment to their mutants via Schism. In this case, though, it felt organic than Civil War thanks to years of tension between Cyclops and Wolverine. Their philosophies differed, especially in the wake of Xavier's dream being eschewed by Scott, and while Cyclops was willing to use child soldiers, Wolverine the Avenger was a new man with new ambitions for peace.

It really flipped the script on both parties as they divided their people and went into battle. Sides were chosen and we ended up having two schools for gifted youngsters from this, giving us a pair of mutant armies with different visions for their future. Marvel also played up personal beef, especially with both men loving Jean Grey, giving us the fight we all wanted to see happen. All was indeed fair in love and war.

14 MUTANT MASSACRE: VIOLENCE UNLEASHED

Wolverine ravaged from a fight in Marvel Comics

Mutant Massacre was a brutal storyline that saw the X-Men and X-Factor dealing with the Marauders who killed a large contingent of the reclusive underground sect called Morlocks. Daredevil, Thor and even Power Pack figured into the plot but it was all made for mutant fans, as it really pushed fan favorites to the limits. Angel (who was crucified) and Nightcrawler were severely wounded in this crusade, which had long-lasting consequences.

Gambit, employed by Sinister, would be caught out for having links to the murderers, while Wolverine also kept the secret of Jean being alive to himself, in a story that was very much based on emotional turmoil. Marvel really played up the massacre angle, especially with Sabretooth as a bloodthirsty Marauder. A lot of flak was garnered because of how violent and brutal the plot was.

13 AGE OF APOCALYPSE: A BRAVE, NEW WORLD

The cover to Marvel Comis' X-Men Alpha #1, which kicked off The Age Of Apocalypse

1995's Age of Apocalypse was an alternate reality ruled by Apocalypse, due to a botched assassination that killed Xavier years before. Nate Grey, aka X-Man (son of Cyclops and Jean), rose up alongside multiple resistance teams, led by the likes of Rogue, Gambit and Magneto, who now stuck to Xavier's mission for peace.

Outside of mutants, Captain Britain, "Thunderbolt" Ross, Hawkeye, Thor, Punisher, Iron Man and Peter Parker, all played key roles in the uprising, making it a comprehensive and unpredictable event. It gave us a dark future where fans realized Xavier was a necessity for his species. It set the tone for contemporary alternate universe stories because it had high stakes and was led by a villain who held nothing back when it came to terminating the opposition. If Marvel wanted to subvert the mainstream, they successfully did it here with this event!

12 NECROSHA: THE BLACKEST NIGHT

X-Men Necrosha

Necrosha continued to show how deadly Rick Remender's X-Force unit was, pitting them against the vampire, Selene. It may as well have been tagged as Marvel's version to DC's Blackest Night as the villainess raised dead mutants as part of an army using the Transmode Virus with Eli Bard. With an X-Force movie in the works, this could be a key source of inspiration too.

What made it click was the controversy over the dead returning and how horrific things played out. It felt like an R-rated comic with Clayton Crain's pencils scaring the life out of us. It tested these heroic mutants on an emotional, as well as a physical level, because having to deal with the dead messes with your psyche and the trauma left did have an impact on Wolverine's posse in the end.

11 OLD MAN LOGAN: FAMILY NO MORE

Old Man Logan drew a lot of heat back in the day for how it portrayed Logan in a dystopian future, forgetting his past as Wolverine. Mark Millar and Steve McNiven gave us an action-packed rollercoaster filled with twists and turns as Logan had to deal with losing a family (yet again), living in a world now overrun by villains, and watching heroes try to cling to past legacies in dust and ash.

With the enemy being the Hulk, who had kids out of incest with his cousin She-Hulk, you'd think that this would be the cherry on the cake, right? Wrong. The revelation of why Logan stopped popping his claws was that he was tricked by Mysterio in the past into murdering all the X-Men. It was a brutal flashback and one that also inspired bits of the recent Logan film. No wonder he's in main Marvel continuity now.

10 THE DARK ANGEL SAGA: ANGEL NO MORE

The Dark Angel Saga was one of Marvel's bleakest arcs with the new X-Force team. Angel was now replacing Apocalypse with his Dark Angel persona in command and the team had to travel to the Age of Apocalypse to get a Life Seed. Dark Beast ended up tricking them and it was left to Psylocke to try to bring the winged X-Man back to the light.

What made it interesting was Fantomex's conscience, left reeling after killing a clone of Apocalypse, and Psylocke's inner-battle with her own darkness and with that of her love in Angel. Rick Remender and Jerome Opena put the team through the wringer and gave us one of the most despicable yet oddly likeable versions of Angel we ever had. He finally turned into a true villain in a story that would end up laying the foundation for the Apocalypse Twins to rise, and for X-Force's destiny to be changed forever.

9 SECOND COMING: DEATH & REBIRTH

Second Coming wrapped the Cable and Hope saga temporarily as it dealt with them returning to the present. X-Force got involved again as Bastion used new Sentinels, as well as villains like Bolivar Trask and William Stryker, to target Hope and the X-Men. Basically, it was all-out war, which cost Nightcrawler his life.

That was just the tip of the iceberg because as the dust settled, Cable made a big sacrifice as well in order to protect Hope. Things ended with a bang as Emma realized she could be the new avatar for the Phoenix, but what really shifted the status quo was the emergence of five new mutants -- The Five Lights -- and the first (outside of Hope) being born since Wanda's M-Day, which otherwise decimated the species. It was non-stop action where everyone was expendable.

8 AVX: A LEGACY IN FLAMES

In Avengers vs. X-Men, years of tension that built up between Scott Summers and Professor Xavier came to a head when the Phoenix Force visited Earth for its new host. Cyclops had alienated mutantkind from the rest of the world by that time on Utopia, and the X-Men went to war with the Avengers over how Hope Summers, seen as the next host for the cosmic entity, should be guarded.

Cyclops and his mutants took it to the Avengers as well, fighting against Wolverine (now seen as an enemy and traitor), and in the process, the Phoenix Force split into five: empowering Scott, Emma Frost, Namor, Colossus and Magik. They became corrupted and were immensely powerful and aggressive. The fight culminated with Cyclops, bearing its full power, killing Xavier, officially ending his old dreams and philosophies of peace. Our heroic mutants weren't so heroic anymore.

7 THE ONSLAUGHT SAGA: DEATH TO ALL

When Magneto extracted the adamantium from Wolverine in the '90s, Xavier lost it and launched a psionic attack on the villain. Their dark psyches ended up combining to give us one of Marvel Comics' most wicked entities, Onslaught. He was pure evil and truly brought out the hatred that Xavier and Magneto harbored for those who despised mutants. What ensued was a scathing war on the X-Men and Avengers that left them dead.

Or so we thought. As controversial as these deaths were, Marvel lodged them in a pocket universe created by Franklin Richards, son of Reed Richards and Sue Storm from the Fantastic Four. This was an even more controversial stroke as it was a literal get-out-of-jail-free card the publisher flipped to outsource the heroes in Heroes Reborn. But hey, whatever works, right?

6 DEADLY GENESIS: A TRUST SHATTERED

Vulcan Marvel

Deadly Genesis left fans' jaws on the grounds when Xavier revealed he had an early team of X-Men who died on a mission in Krakoa. The team included Cyclops' long-lost brother, Gabriel, who emerged from the shadows to play mind games. He came back as Vulcan, an energy-absorbing and near-omega level mutant, filled with hate towards the Professor and his charges.

Vulcan's battle with Cyclops also pulled no punches as he was jealous and spiteful that he never achieved his full potential as an X-Man. The revelation was a major stroke in breaking the bond that Scott and Xavier shared, the further erosion of which led to him killing his mentor in AvX years later. We witnessed a shocking side of Xavier, especially as he mind-wiped his students so they would forget about the botched mission. His integrity was very much shattered at this point.

5 MESSIAH COMPLEX: A NEW HOPE

Messiah Complex was a crossover event that involved a lot of players, while picking up from Scarlet Witch's de-powering of the species. The Purifiers, Marauders and a new hunter called Predator-X played a part as everyone searched for the first mutant (Hope Summers) born since Wanda's M-Day. Bishop tied in as well as he wanted her dead because he saw the child as a destroyer in the future.

Cable was the hero, fending off all attackers, in order to save the baby who he viewed as the mutant messiah. Cyclops allowed him to escape with her into the time-stream as he bought into Cable's theory of Hope being a savior. They made a lot of enemies in the process but it gave us Cable at his very best and teased a bright and Phoenix-filled future for mutants.

4 IVX: FIGHTING FOR OUR SPECIES

Inhumans vs X-Men with Magneto and Black Bolt leading their teams

The Inhumans vs. X-Men event was a tough one to pick a side for because both teams had just cause. The Inhumans, in the wake of Thanos' attack in Infinity, unleashed a Terrigen Bomb over Earth in order to grow their population by exposing dormant Inhumans to Terrigen Mists. However, these clouds were lethal to mutants, which gave us a shocking reveal that Cyclops died from exposure.

One species needed it to survive while it proved genocidal to the other. No wonder Emma Frost faked Cyclops being alive, tricked Black Bolt into killing him, then waged war against the Inhumans. To make things worse, kids were used on both sides as warriors! Medusa also stepped up as a war tactician, really making this a war of queens to preserve their species. Magneto and Emma regressed a bit, touching base with their villainous ways once more.

3 MESSIAH WAR: EVERYONE'S THE ENEMY

Messiah War followed up Messiah Complex and took the X-Men on a brutal trip. Cyclops sent his murderous X-Force unit into the time-stream after Cable and Hope, but they found themselves torn in a war between Stryfe (a Cable clone) and Apocalypse. Cable's old team was now led by Wolverine and included former lover Domino, Deadpool and Archangel among the ranks, shifting the team into a much more lethal mode of operation.

X-23 also turned it up in terms of her killer instinct and this was one of the events that made Wolverine question if Cyclops' new way of protecting mutants was worth it. Cable went on the offensive like never before, ready to protect Hope at all costs, even if it meant killing fellow X-Men (or Bishop). The kid gloves came off and the mutants had no more lines drawn between friends and foes.

2 THE DARK PHOENIX SAGA: ODE TO JEAN

Dark Phoenix Byrne

The Dark Phoenix Saga is so powerful that it inspired X-Men: The Last Stand, and now Fox is throwing us a Dark Phoenix reboot. This story is one of the most revered in comics history as it shows the duality in every hero who is struggling with good, evil and true power. Jean Grey became the host for the Phoenix Force, and when she became corrupted, all of the Marvel Universe felt her wrath.

Galactic genocide ensued, cosmic empires went after her and throughout it all, her X-Men tried to redeem her. It was also a deep love story as Cyclops believed in her but things ended up quite tragic as Jean lost her life in the battle to save her soul from being consumed by this dark power. The story tainted a hero but still showed us resilience and hope down to her final breath.

1 HOUSE OF M: NO MORE MUTANTS

no more mutants

House of M turned heads because of how Brian Bendis and Olivier Coipel painted such a compelling alternate reality where Magneto ruled as a monarchy with his kids. Mutants and Avengers alike found themselves in new and somewhat unfamiliar roles, giving us the cliched story of a rebellion rising. That said, it was well done and made even better by the reveal of Scarlet Witch being the one who created this world.

Further to that, it wasn't Magneto but Quicksilver, Wanda's brother, who pushed her into this. This led to a couple key "deaths," but it more or less justified the Avengers for wanting to kill her prior to this because she was very much a ticking time bomb. The status quo was well and truly changed when she reset things via her "No More Mutants" line, rendering her species nearly extinct.

Let us know in the comments which X-Men event or storyline truly left a controversial mark on you!