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HK-47 - as seen in Star Wars: Knights of the Old Republic I and II

The devil really does have the best tunes - HK-47’s snarky dialogue stole the show in the otherwise very serious KotOR. The careful parallels with C-3PO were what made him great: Star Wars’ most camply irritating character redrawn as a merciless killer with a razor-sharp wit. “‘Love’ is making a shot to the knees of a target 120 kilometers away using an Aratech sniper rifle with a tri-light scope,” he quips, or “If I see one more idiot attacking a Jedi with a blaster pistol, then I’ll kill them myself.”

Hitler - as seen in Wolfenstein 3D

Nazis maybe all over the place, but getting to fight Hitler himself is rare; especially when he’s wearing a giant robot suit with chainguns for arms. Still, the fact he turned up here wasn’t much of a surprise, given that the episode of Wolfenstein 3D in question was called “Die, Fuhrer, Die!” Oh, how we miss id Software having a sense of humor.

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Ignus - as seen in Planescape: Torment

Whether Ignus is a villain or not is open to interpretation, but given his history of killing sprees, it’s safe to say he’s probably not big on charity work. First seen as a living statue imprisoned as a table decoration in the aptly-named Smoldering Corpse Bar, this powerful mage can be freed from his stasis to join the party. It turns out he’s utterly, hopelessly insane, riddled with paranoia and hatred, and obsessed with burning stuff. Say the wrong thing and he’ll attack you; say the right thing and he’ll just threaten to attack you. Bring him with you for the final battle and, convinced that you’re responsible for his unhappy state, he’ll turn on you anyway. Not a nice guy.

Irenicus - as seen in Baldur’s Gate II

Joneleth Irenicus is a fallen elf who’s had his pointy ears surgically removed. That’s pretty twisted - as is his tendency to insta-kill people by the half-dozen and swap souls with someone whose destiny he likes the look of. His evil is of a particularly grand kind - he wishes to harness the power of the gods themselves, and doesn’t particularly intend to use it to end world hunger when he has. Many of his massacres are also because he seeks revenge for a lost love - but hey, who hasn’t done that? The opening hour of the game will make you hate him forever.