C is for Chimeras
Chimeras are critters that are made up of the parts of other critters. The classical Chimera is obviously the terrifying creature you can read about in Greek mythology, which is a mishmash of 3 different animals: a lion, a goat, and a snake. The Chimera was able to breathe fire, and just being unfortunate enough to see the damn thing was a bad omen that apparently suggested you were gonna get fucked up by nature. What an asshole.
Well, that hasn't changed one bit. Chimeras in games are damn sweet enemies...and I'm not just talking about the rehashes of the creature from myth. There are also numerous games with cronies and enemies that are chimeras of other different animals or organisms. For example, Mother 3's Pigmask Army has the creation of chimeras from various animals in the wilderness as one of their main objectives. Super C's final boss is some weird mashup of...a human face, some fucked up alien, a spider, and a toad or something. A lot of Final Fantasy enemies resemble combinations of animals or monsters, as well as tons of disturbing bosses from various other video games.
Oftentimes, chimeras in games are disturbing to even look at or think of, which makse them a damn good cronie to begin with. Chalk up the fact that these things are usually pretty damn tough and will often have abilities attributed to each animal you can see in the organism, and you've got a fearsome, creepy, and irritating enemy that you really have to think about before you tackle.
D is for Demons
These guys are jerks, but the best thing about demons is that you never, ever feel bad about kicking their asses.
Perhaps the most iconic instance of demons in video games is in the Doom series. Demons start to invade UAC bases on Phobos and Deimos (the moons of Mars) via the use of portals that apparently link directly to hell. These guys come in all shapes and sizes, from the humanoid fire-hurling Imp, to the floating, one-eyed, basketball-shaped Cacodemon, to the towering Cyberdemon, which is a cybernetic goat...thing...that's about 20 feet tall and sports a rocket launcher for an arm. Do I need to say anything else?
Well I will.
Throw in terrible enemies like the Red Arremer from the Ghouls N' Ghosts games if you really want to cry. These assholes are some of the dodgiest, most persistent enemies you'll ever encounter and they frustrate me just thinking about them. The Devil May Cry series is loaded with demonic assholes to punish, as well as Ninja Gaiden for the NES which involves a demon king named Jaquio trying to create a DEMON ARMY. HOW MANY TIMES HAVE I SAID THE WORD DEMON SO FAR?
Hellish brutes from Blood that you set alight with a flare gun...pretty much any major enemy from the Diablo series...
Yeah, demons are abundant in games. They can take many forms, have many different attacks, and are generally just one of those enemy types that no one has a beef about when it comes to putting them down in a bleeding mess on the floor. Load up your Plasma Rifle and get to it.