1 Aku - Samurai Jack
Aku is a fictional character and the main antagonist of Samurai Jack, an American animated television series created by Genndy Tartakovsky for Cartoon Network.
2 Mojo Jojo - The Powerpuff Girls
Mojo Jojo is a fictional character from the American animated television series, The Powerpuff Girls, created by animator Craig McCracken for Cartoon Network.
3 Plankton - Spongebob Squarepants
Sheldon James Plankton, or simply Plankton, is a character in the Nickelodeon animated television series SpongeBob SquarePants.
Even though he has been bogged down in the newer seasons, if you look back at the original 3, and I'll even say season 4, he was pretty mean and really funny. Take the first movie into account, and he truly is a terrifying villain.
4 Slade - Teen Titans
Slade is a fictional incarnation of the character Deathstroke in the American animated series Teen Titans and is the archenemy of the Teen Titans, who wants them destroyed for his own unknown reasons, and is the main antagonist of Season 1 and Season 2; He appears as a vision in Season 3, returned only ...read more.
Probably one of the first cartoon- anime influenced shows I watched. I always remembered how evil and vengeful Slade was and still is. He puts up more of a fight then the other villains on Teen Titans. Half of his dialogue is memorable enough said.
Wait until TTG ruins him - TwilightKitsune
I love Slade
5 Denzel Crocker - Fairly Odd Parents
Denzel Quincy Crocker is a fictional character from the American animated series The Fairly OddParents created by Butch Hartman for Nickelodeon. He is the mentally unstable school teacher of Timmy and is one of the main antagonists in the series.
6 Father - Codename: Kids Next Door
Father: "You... big... JERK! Now you've made me angry. VERY. VERY. VERY... ah, forget it." - ModernSpongeBobSucks
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7 The Flying Dutchman - SpongeBob SquarePants
The Flying Dutchman is a recurring character in the Nickelodeon animated television series SpongeBob SquarePants.
He was a villain? I never knew lol. - Catacorn
8 Vlad Plasmius - Danny Phantom
Vladimir "Vlad" Masters (also known as Vlad Plasmius) is the main antagonist from the American animated series Danny Phantom created by Butch Hartman for Nickelodeon. He is Danny's arch-enemy and Jack Fenton's former best friend and Maddie's former lover. He is voiced by Martin Mull.
9 Katz - Courage the Cowardly Dog
Katz is a fictional character from the Cartoon Network animated series, Courage the Cowardly Dog. He frequently appears as a recurring antagonist in the series . His first appearance was in the episode "A Night at the Katz Motel" .
Yes! He was such a cool villain. The episodes where he's the antagonist were my favorite. And his theme song was creepy as heck but awesome!
10 Professor Calamitous - The Adventures of Jimmy Neutron: Boy Genius
Professor Finbarr Calamitous (simply known as Professor Calamitous) is a fictional character and the main antagonist of The Adventures of Jimmy Neutron: Boy Genius.
11 Azula - Avatar: The Last Airbender
Princess Azula is a fictional character and antagonist of Nickelodeon's animated television series Avatar: The Last Airbender.
12 Van Kleiss - Generator Rex
13 Ozai - Avatar: The Last Airbender
Fire Lord Ozai is the main antagonist of Avatar: The Last Airbender. He is the supreme antagonist of the series due to being in control of the Fire Nation and being the father of Zuko and Azula. He is also Aang's arch-nemesis.
He should be #1
14 Nergal - The Grim Adventures of Billy & Mandy
15 Vilgax - Ben 10
Vilgax is a fictional character and one of the main antagonists of the American animated TV series and media franchise Ben 10 created by Man of Action Studios and produced by Cartoon Network Studios.
16 Nicolai Technus - Danny Phantom
Nicolai Technus is a fictional character in the American animated series Danny Phantom created by Butch Hartman for Nickelodeon.
17 The Lich - Adventure Time
The Lich (formerly named the Lich King in the original pitch and "His Hero," and referred to as Sweet Pig Trunks in his baby form, or just Sweet P for short) is a powerful undead being and a major antagonist in the American animated series Adventure Time.
18 Dan Phantom - Danny Phantom
Dan Phantom is a fictional character in the American animated series Danny Phantom created by Butch Hartman for Nickelodeon.
19 Mandark - Dexter's Laboratory
Susan "Mandark" Astronomanov is the main antagonist in the American animated series Dexter's Laboratory. He is Dexter's rival and later mortal nemesis who often seeks to destroy both Dexter and his lab to prove once and for all that he is the superior genius. He is voiced by Eddie Deezen.
20 The Chameleon - T.U.F.F. Puppy