Hopefully this won't be too much grasping for straws
Drakken/Doofenshmirtz: Guess it's because they're both Disney villains, but they're similar in that they're both mostly harmless comical villains, who are considered butt monkeys in their respective series, with a variety of inventions but with rather petty goals
I treat all living things equally. That is to say, I eat all living things
King Koopa and Dr Rrrrobotnik.
Both quirky buffoonish villains of Di C-made video game adaptations, often using cliche slapstick inventions in their attempts to destroy them. Some similarities are less than subtle ("I hate those plumbers"/"I hate that hedgehog"), to the point they even use the same schemes and plots in particular episodes. Despite this due to their humor value and Chewing the Scenery to every level they arguably steal the show from the heroes themselves.
They also share the odd trait of being drastically altered from their game counterparts cosmetically, yet having some amazing similarities to how the latter would eventually develop.
Shut up!
Megatron and Scar. Both want power and will do almost anything to get it, and both are very melodramatic and charismatic. They also both know that their respective enemies (Optimus Prime and Mufasa) are not to be trifled with and that scheming is a better way to defeat them than to challenge them directly.
edited 17th Jan '13 9:54:19 AM by resetlocksley
Fear is a superpower.
Psi 001, I think some of Koopa's live-action portrayals are even more Eggman-like than that!
Skeletor and Mumm-Ra. Both undead, both wizards, both evil leaders of less-than-competent monster minions. Though Mumm-Ra always came across as smarter (and more evil) than Skeletor.
...Come to think of it, there have been a lot of villains like that. Skullmaster, Venger from Dungeons & Dragons (I think? Never was sure if he was undead or not) etc.
edited 17th Jan '13 2:48:59 PM by Sijo
MASTER OF BIG RED
Zuko and Ice King: Both have elemental powers. They both are part of royalty, and they both seem to have anger issues. They both also have/had a teenager and an animal defeat them multiple times. Both of them also helped the hero who they fought. Both of them were revealed to have sad backstories. They were both also involved in a war (and it is heavily implied that Ice King started the war). They also both have an army of people who never seem to do anything right, and they both have a companion (Zuko has the fire army and Iroh, Ice King had his penguins and Gunther). Finally, they both ended up living with the hero.
BIG RED 4 LIFE
Let's play a little game, where we compare villains and their appearances, plans and motives.
edited 13th Jan '13 7:36:44 AM by Disney23