Since cartoons have become more mainstream and versatile, cartoon villains have grown into more engaging characters full of depth. In the cartoons of this millennium, the greatest villains have unique and compelling motivations. They've also managed to triumph over the hero from time to time.

These iconic villains have stuck with fans because of how much they bring to the series, whether it's stirring drama, intense action, or a challenge the hero never realized they needed. Though it can be hard to watch the hero suffer at the hands of the villain, the best villains are the most thrilling to watch.

10 Samurai Jack: Aku Already Reigned Supreme By The Start Of The Series

The hero of Samurai Jack spends his entire life training to defeat the demon Aku, who's already started his evil reign. Right before Jack lands the finishing blow, Aku tears a portal in time and sends Jack into the future, giving the demon the time he needs to fortify his supreme control.

What makes Aku so memorable isn't just his overwhelming abilities or his haunting laugh, it's his brilliant mind. Aku is aware he's about to be killed by Jack, but rather than a monologue or making a last attempt to kill Jack, Aku takes the more strategic approach. Because of his balance of strength and strategy, he's a formidable adversary, and even more so, an unreachable obstacle Jack struggles to overcome for almost the entire series.

9 Voltron: Legendary Defender: Lotor Defines What A Complex Villain Should Be

In any large-scale war, leaders will have clashing ideals, but it's rare for a cartoon to reflect that. Voltron: Legendary Defender started out as very simple in its contention between the heroes and villains. That is, until Prince Lotor was introduced. While his father, Emperor Zarkon, took an oppressive approach to his galactic conquest, Lotor appeared diplomatic and compassionate, though it was all a ruse.

Lotor chose to manipulate people to gain support and power for his own plans to abuse Quintessential energy. In his mind, he was a hero giving people what he felt they were owed, though he failed to see how his tactics hurt people and only served himself. Lotor had everyone fooled until his last moments, adding a complex layer of drama to make the show more engaging.

8 Over The Garden Wall: The Beast's Greatest Power Lies In The Unknown

Many villains use manipulation as a tactic, but with limited exposition throughout Over The Garden Wall, overcoming The Beast's manipulations becomes a traumatic experience for the heroes, yet a thrilling engagement for the audience. The Beast convinces their target their worst fear of losing a loved one will happen if they don't keep his lantern lit, which takes advantage of the victim's anxieties and pessimism.

This villain's manipulation is so central to the series' existential conflict of learning to have hope and think more positively – something the protagonist Wort struggles with. The Beast knows how to isolate their victims and leave them with little to no details of themselves, and it's this control over knowledge and mystery that's so haunting to watch. It makes the villain unforgettable.

7 Owl House: Emperor Belos Has An Entire Kingdom To Boast His Name

With the masses on his side, believing him to be a righteous ruler, Belos assumes no one would oppose him. This makes the heroes' journey that much harder in The Owl House. Much of what Emperor Belos shows his subjects is riddled with lies and deceit, but to what end remains a mystery even as the series nears its end. What really makes Belos a compelling villain is how adored he is, and for good reason.

The people have learned to live with Belos' laws, and there's little contention between the Emperor and his people. He appears very kind, even choosing to spare his enemies if enough of his people ask. The bottom line is: he doesn't need to kill off his enemies to secure victory, since his control over the Kingdom is already enough to help him achieve his goals.

6 Legend Of Korra: Amon Was Korra's Worst Nightmare

When first introduced in the Legend of Korra, Amon had a terrifying but unique idea of changing the world for the better by taking away people's bending abilities. His conviction and raw strength were enough to make the hero, Korra, uneasy, but the brash young teen wouldn't cave into the fear and tried to face Amon head-on.

During Korra's challenge, Amon ambushes her and threatens to take her bending, further instilling fear into the Avatar. However, he leaves her alive and unharmed, at least physically. This scene cements Amon as a great villain. His aim isn't just to beat the Avatar; he wants to destroy their reputation. By leaving Korra in fear of him, he tears her down enough to make a statement to the world.

5 Gravity Falls: Bill Cipher Brings Just Enough Humor To Villainy

What kept viewers watching Gravity Falls was the mystery and the compelling characters, and at the center of it all was the villain Bill Cipher. Throughout season 2, it becomes clear Bill is more than just a wise-cracking antagonist; he is the villain to beat.

As his fearsome powers became more apparent and his actions grow more heinous, the tension of the series rose. But even as Bill became the main villain, he was also rather likable. His charisma and quips separate him from typical villains who take a more straight-laced approach to manipulation and conquest.

4 Adventure Time: The Lich Is The Immortal Nemesis Of Heroes

He may not be the final villain of the series, but the Lich is widely known as one of Finn and Jake's greatest enemies in Adventure Time. Beyond his terrifying appearance, the Lich leaves a haunting mark on viewers because of how powerful it is.

This literal embodiment of evil doesn't even need to throw fists to spread chaos, as there have been plenty of moments his mind games were more than enough to crush the good guys. The only character strong enough to stop this heinous creature is Finn. However, with every win against the Lich, the villain manages to remain in some state of being, lying in wait to destroy all that's good in the world.

3 She-Ra: Catra Is A Twisted Commander Of Injustice

In She-Ra and the Princesses of Power, Catra is a unique villain whose motivations are mixed with raw emotions, which make her surprisingly sympathetic and likable. She's fully aware everything she does is morally wrong, but she outwardly states how little she cares. Still, the show leaves room for her redemption even as she falls deeper.

Normally, a villain with such low morals would be hated by fans, but Catra's playful personality paralleled with her tragic backstory made her a rounded and engaging character to watch. With so much potential for good, she chooses to do the wrong thing, and her fall from grace serves as one of the most engaging parts of the series. Her villainy alone – supported by her impressive fighting skills and cunning mind – is captivating to watch, as her actions become more devastating with each conquest.

2 Korra: Zaheer Went Where No Cartoon Villain Has Gone Before

Forging his own way to reform the world, Zaheer is the leader of the Red Lotus, whose goal is toward anarchy against the Four Nations, the White Lotus, and the Avatar. In Legend of Korra, his extremism is put to a stop when he and his allies are imprisoned, though they eventually escape.

Zaheer initially thrived on his martial arts, but after he's suddenly gifted with airbending abilities, his newfound strength helps to free himself and his allies. Within the lore of the series, Zaheer's threatening presence as an airbender is new for the setting, which initially painted airbenders as pacifists. This unique aspect of his character, along with his calm demeanor in the face of bloodshed, is what makes him so impactful as a major antagonist.

1 Last Airbender: Azula Is The Greatest Threat Throughout The Series

Normally, it's the main antagonist who's seen as the villain to beat, but in Avatar: The Last Airbender, the most fearsome enemy is Azula, the daughter of Firelord Ozai. No matter where Team Avatar run, Azula is trailing behind them, ready to wreak havoc in name of the Fire Nation, though it was clear she relished stepping over others.

Her over-confident personality is rewarded by her numerous victories, which only build up her terrifying presence. She always has the right idea to achieve victory, even if it means dirtying her own hands.