One of the challenges of an action game is creating a villain that you, the player, will want to destroy. Some games, like Killzone 3, end up crafting bad guys so cool and awesome, you're rooting for them instead of the so-called heroes. Then there are games that just get it right, making an entire army of bastards you just want to punch in the face.
Thanks to a mixture of visual design, atmosphere and writing, some games go beyond even that, and are able to craft an entire race of enemies that are simply despicable to behold. They're ugly, they're disgusting, and they garner absolutely zero sympathy. Those are the truly successful baddies in videogames, and now we rightly pay tribute.
When it comes to plain old ugly, very few enemies do it better than the Locust. These subterranean barbarians are the primary antagonists in Gears of War, and while they come in many varieties, the running theme across the entire species is pure visual abomination.
They resemble reptilian apes, with squashed, pug-like faces, snarling mouths filled with uneven teeth, and an apparent belief that we want to look at them topless. Their women are twelve-feet tall and have faces closely resemble Castle Greyskull carved out of dry dogshit.
Gears developer Epic did a wonderful job with the Locust, crafting an enemy that is at once very humanoid, yet utterly alien to us. Even their voices, gutteral and with a limited grasp of English, are both familiar and obscene. They are like people, but primordial and brutish. They are ugly because they're like parodies of us, and that somehow makes them even less sympathetic than something completely inhuman.
Imagine the twisted offspring of a Borg and a zombie. Undead constructs of flesh and metal, built by something that placed pure function well above any aesthetic value. That is the Strogg, the techoflesh empire that acts as your principal foe in Quake II and Quake IV.
The Strogg were designed entirely to be horrific, and the art department deserves a golf clap for the effort. Unlike the Borg, which still manage to look rather sleek and stylish, the Strogg are twisted Clive Barker freaks that dredge up images of torture and sheer, uncompromising brutality with their very presence.
As mindless soldiers bred only for war, a Strogg soldier doesn't care that weeping sores and gaping, blood-soaked wounds cover its flesh. It doesn't care that pipes are jammed into its throat and jagged spikes are protuding from its swollen belly. Unfortunately, we care, and that's our disadvantage. The mere thought of the Strogg is enough to make one feel queasy.
Take the Strogg, but replace the metal parts with jagged, bony, mutated parts, often attached in all the wrong ways. You now have the Necromorphs from the Dead Space universe. Unlike your average zombie, the Necromorph has been warped and twisted to such a degree that it is barely recognizable as human.
Upon close inspection, however, the human aspect is made all too clear, and it's heart-rending. Pained, glassy-eyed expressions on skewed mockeries of faces and arms torn open for new limbs to arrogantly sprout in their place. The artists at develoer Visceral have an incredible talent for designing Eldritch, babbling, disturbing creatures, and it shows with every member of the Necromorph race.
The worst part of the Necromorph design is, of course, the fact that it applies to children as well. Babies and juveniles both appear in Dead Space 2, and despite their monstrous appearance, they still somehow resemble kids. To pull that off takes the kind of skill that no sane human would willingly desire. There it is, though -- Visceral made something that is hideous, yet child-like. The juxtoposition results in something utterly grisly, something that hints at a force with truly no compassion.
The Space Pirates
The design of Metroid's Space Pirates has varied considerably over the franchise's many games, but the fleshy mistakes from Metroid Prime 3: Corruption are arguably the most grotesque interpretation. Their heads are eyeless, meaty balls of sharp fangs and mandibles, and the skin looks like it would be sticky to touch.
Space Pirates have always looked somewhat unpleasant, and that was taken to eleven with Corruption's slavering fiends. How in the universe do they function in everyday life looking like a cross between a dog's penis and a frozen afterbirth? It doesn't bear thinking about.