The Green Lantern Corps is full of great characters, but John Stewart is easily one of the best. An ex-Marine sniper, John brings an air of military precision to the Corps that some of the other human Lanterns lack and because of his experience as an architect, his ring constructs are some of the most meticulous and intricate. Hal Jordan gets all the love, but John is just as good and is currently the Green Lantern of the Justice League.
One of the toughest Green Lanterns around, how would John fare against the villains of the Marvel Universe? Which ones would he defeat? Which ones would defeat him?
10 Would Lose To: Baron Mordo
One of Doctor Strange's most powerful enemies, Baron Mordo was almost Sorcerer Supreme until Strange came around and outclassed him. Don't think this means he isn't powerful, though- Mordo has still almost ended Strange on several occasions and is still one of the most powerful sorcerers around.
Both men would be able to protect themselves from the other attacks, but Mordo's magic gives him way more options to take John out. It might take a bit, but John is going down.
9 Would Defeat: Doctor Octopus
Otto Octavious and his thought linked robot arms are no joke. Constantly fighting Spider-Man, over the years he has proven himself to be one of the Web-Slinger's greatest foes and was even able to defeat him, taking over his body and proving his superiority.
Against a lot of heroes, Ock is a challenging, but against John Stewart? Yeah, there's not much that Ock could do offensively against John, whereas John has tons of options. This fight is pretty much completely unfair as John can protect himself indefinitely from Ock and hit him back in ways that Ock has no answer for.
8 Would Lose To: Shadow King
The Shadow King is one of the most dangerous telepaths on the face of the Earth. Residing on the Astral Plane, his desire is nothing less than taking over every mind on the planet. Able to stand up to some of the most powerful telepaths on the X-Men, Shadow King is a force to be reckoned with.
Shadow King does most of his combat on the Astral Plane. John's willpower would allow him to make a good accounting of himself... if Shadow King gave him a chance to get his bearings and figure out how combat works on the Astral Plane. John just wouldn't be able to defend himself and that would cost him the fight.
7 Would Defeat: Avalanche
A former member of Mystique's Brotherhood of Evil Mutants, Avalanche is able to generate seismic waves that allow him to not only create earthquakes but destroy buildings and basically mess up the day of anyone he hits them with. Avalanche has been able to singlehandedly give both the Avengers and X-Men a good fight.
John can fly, so any earthquakes Avalanche causes wouldn't affect him. His shields would protect him if Avalanche tried to attack him directly as well. Avalanche really doesn't have much he could do to John, while John could take him out in any variety of ways.
6 Would Lose To: Loki
The God of Mischief, Loki has been causing trouble for the heroes of the Marvel Universe since the beginning. His threat is the one that brought the Avengers together and he has been a thorn in the side of his brother Thor for millennia. Strong enough to punch it out with his brother Thor, he's a master of magic and trickery.
Being a Green Lantern means that John has amazing willpower, but it won't do much against the power of a god. Loki's trickery based magic would too much for John and he would probably be able to convince John to give him the Green Lantern or at least let down his defenses long enough for Loki to take him down.
5 Would Defeat: Green Goblin
Spider-Man's arch-nemesis, Green Goblin is as brilliant as he is insane. His Goblin formula gives him superhuman strength, agility, and a healing factor and his Goblin glider and pumpkin bombs give him all kinds of offensive options. He's proven that he can contend not just with Spider-Man, but even with the Avengers as well.
Against Spider-Man, Goblin is a dangerous opponent but against a Green Lantern, there's really not much he can do. John could defend himself from any of Green Goblin's attacks and his ring allows him to be much faster and more maneuverable than Goblin. It wouldn't take long for John to take him down.
4 Would Lose To: The Void
The dark side of the Sentry, the Void is one of the greatest threats the Marvel Universe has ever faced. Gifted with all of the same powers of the Sentry, the Void is malevolence given form, all of the insanity of Bob Reynolds with none of the man's goodness. The Void is a world-ending threat, able to take on teams of Avengers without much trouble at all.
The Void would be a challenge for the entire Green Lantern Corps, so against one Green Lantern, even one as skilled and powerful as John? The Void would just be too much for him.
3 Would Defeat: The Mandarin
The Mandarin is a Chinese warlord who one day came across a crashed alien ship. Inside, he found ten rings of power, each with a different ability and used them in his bids to take over the world. Iron Man has been able to stop his schemes, but the Mandarin is a deadly threat regardless.
Mandarin's ten rings are pretty impressive, giving him a wide range of attacks to use but John just needs one to beat him. The Green Lantern ring will allow him to defend himself against the Mandarin and create constructs that would take Mandarin out.
2 Would Lose To: Doctor Doom
Doctor Doom is the greatest villain in the Marvel Universe. Thanos? Doom laughs at Thanos. Apocalypse? Doom is the fittest. Kang The Conqueror? Doom will teach him a lesson in conquest. One of the smartest men on planet, a skilled sorcerer, and possessor of the most powerful suit of armor, none rival Doom. Just ask him, he'll tell you so himself.
Doom's armor has allowed him to drain the energy of Watchers, the Silver Surfer, and the Beyonder. He would do the same to John's ring, leaving him powerless against Doom. At that point, the fight only lasts as long as Doom wants it to and he'll gain a Green Lantern ring in the process.
1 Would Defeat: Ultron
Created by Hank Pym, Ultron is easily the most frightening foe the Avengers face. With am outer shell of adamantium and strong enough to contend with even the most powerful Avenger, Ultron has decided that the human race needs to die and will stop at nothing to kill every person on the planet.
John would eventually realize that his attacks couldn't hurt Ultron's outer shell... but he could hurt him from the inside. John would just create a few constructs within the mad android and tear his systems apart from the inside.