C

Conroy Bumpus - as seen in Sam & Max Hit The Road
Elvis by way of Garth Brooks and Prince Phillip, wig-wearing Conroy is the nastiest piece of work in a game where everyone is at least slightly malevolent. Worth a fortune thanks to hit records such as “Let’s Get Drunk and Shoot Things” and “Heaven’s Just Like Texas, Except That There’s No Taxes,” he can now afford a life of collecting rare wildlife to either kill, stuff and rig with robotics, or force to play in his backing band. In his own words, “I’m just a warped evil person who gets his jollies torturing cute woodland creatures.”

Cyberdemon - as seen in Doom, Doom II, Doom 3, various expansions
The Cyberdemon is the best example of Doom’s mentality of absolute excess. Ten feet tall, a rocket-launcher for an arm and miscellaneous techno bits built into its Minotaury body, it’s utterly ridiculous, and the template for a lot of far less entertaining rip-offs. A secret level in Final Doom features 13 of the jerks in one room - circlestrafe for your life, boy.

D

Diablo - as seen in Diablo, Diablo II and various expansions
Who knows what postgraduate course Diablo had to take to earn his “Lord of Terror” title, but it suits him. After all, this is a demon that can only be defeated by someone bashing a hole in their own head with a magic rock and then absorbing him into their soul. And even then, Diablo just takes control of the poor bastard and heads off on a fresh rampage, rendering the 20-odd hours they’ve just spent trying to save the world from evil somewhat pointless. Nice guys always finish last, eh?

DomZ - as seen in Beyond Good & Evil
There’s nothing quite as effective as a baddie with a plan (as opposed to simply “Hey, I feel like killing some stuff”), and these cruel, calculating aliens certainly have a grand design. It involves capturing everyone on the planet and either mutating them into mindless drones or sucking the life out of them, which is an admirably completist goal. Also, they kill a friendly pig, which is just mean.