4. Nemesis (Resident Evil 3)
Nemesis is easily one of the most formidable and ground-breaking foes in any video game, pushing the envelope in terms of intensity and game mechanics, for he pursues the player from the start of the game right through to the climax. Like Mr. X in the previous Resident Evil game, Nemesis appears usually at the most inopportune moments, wasting whoever is in the vicinity, and frantically running after Jill, able to chase her through doors, while shouting "STARS!" and firing his trusty rocket launcher. Though you could choose to either fight him or flee, fighting him would often just prove a waste of ammo, even if the alternative was at best stressful and at worst, bloody horrific. This was Capcom at some of their most inventive, doing away with the idea that once you get past that door-opening loading screen, you're safe from whatever is behind it. Nemesis, with his super strength and sublime speed, remains one of the most imposing and terrifying enemies in video game history, and one that the series itself has never topped.