Boss fights typically go one of two ways. You might see them as chances to test your skills or to learn about a monster's history, but you could just as easily view the fight as a roadblock, prohibiting true game progress. No matter which camp you fall into, both sides can agree on one thing: recurring bosses are a nightmare.
Whether it's because the big baddie's appearances are truly intense or simply annoying, recurring boss fights are a pain. Some bad guys just don't quit, stalking your heroes and showing up for battle at the most inopportune times. These are some of the worst offenders.
SA-X (Metroid Fusion)
The SA-X is like humanity's fear of viruses made flesh. When space adventurer Samus' suit is infected by the X Parasite during the opening of Metroid Fusion, pieces must be removed and quarantined. But the parasite fuses them back together to make a shadow version of Samus herself. Even worse, that suit was completely upgraded: the SA-X is a fully loaded, fully evil clone.
This unstoppable beast then roams the halls of the research station, running into you at what feel like the worst possible times. All you can do is run and hide, frantically searching for a way to escape from the parasite's deadly Ice Beam. Luckily, the SA-X finally falls after several of these cat-and-mouse encounters, overwhelmed by a swarm of baby Metroids.
Or does it? As you quickly find out, there are no fewer than 10 SA-Xs out there -- they reproduce asexually. What's worse than an unstoppable dark version of yourself? A whole army of you.
Thankfully, a fully upgraded Samus is an equal match for the maxed-out SA-X. With the same weapons and abilities, you can finally take down your clone before destroying the research center itself. And even then, that darn Parasite escapes… only to later come to your rescue, teaming up to stop the indomitable Omega Metroid. Survival of the fittest, indeed.
Gary Oak (Pokemon Red & Blue)
Pokemon is a series of pure escapism. What better way to disappear for a bit than to slip into Kanto or Johto and breed some adorable Poke-babies? Shame you still have to deal with bullies like Gary Oak (or whatever name you choose for your rival), pestering you with unfair battles at every turn.
First, he picks whichever starter Pokemon is super effective against the one you've already chosen. We throw out "rock, paper, scissors" simultaneously for a reason, people. Then he stops you for battles about half a dozen times during your journey. When you manage to overcome the master trainers that are the Elite Four, you enter the final room to face the Pokemon Champion -- it's Gary again! Professor Oak's nephew is a real jerk, but at least he gets his just desserts in that final Pokemon duel.
Nemesis (Resident Evil 3: Nemesis)
What's worse than a rival? A nemesis. The Nemesis T-Type is a smarter, far more powerful version of Resident Evil's Tyrant. You know, the guy who required a rocket launcher to the face to be killed. He's sent into Raccoon City to make short work of the S.T.A.R.S. team investigating the metropolis.
It's tense enough guiding Jill Valentine through the horrors of the city, pegging zombies and solving color-coded puzzles. But then you get the horrifying Nemesis stalking you, appearing in random corridors. He kills poor helicopter pilot Brad Vickers with a tentacle through the head, and even destroys Jill's escape chopper at the city's clock tower. The dude does not like air transportation.
Oh, and all this happens while the Nemesis is in his first form. After a firefight near the chopper wreckage, he returns in a second, extra nasty, tentacle-covered skin. Several random appearances and a fall into a chemical pool later, he's gone for good.
Nah. He wriggles after Jill and infects a nearby Tyrant, somehow becoming even more powerful than before. Fortunately, a few rail gun blasts to the body and bullets to the brain finally fell the killing machine. The master of unlocking is a pretty good monster-killer too.
Big Sister (BioShock 2)
Remember those adorable, albeit disturbed Little Sisters that run around Rapture in BioShock? They don't stay cute forever. Big Sisters are all kinds of messed up thanks to their exposure to ADAM, making them seven feet tall and super athletic. They run the show in BioShock 2, stopping at nothing to kill off Subject Delta as he searches for his own Little Sister.
No fewer than seven of these menacing ladies will bust through the walls of Rapture to hunt you down. And who knows how many are actually out there? A pair of them double team you as you reach your former companion Eleanor Lamb, a final challenge to cap off the other deadly encounters. The good news? Eleanor herself dons armor to become a much tamer Big Sister, helping you escape.
Maybe it would have been easier to harvest all those Little Sisters after all?
Liquid Snake (Metal Gear Solid)
If we're talking about bosses, we have to bring up the son of Big Boss, right? The love for son number one, Solid Snake, is strong, but his twin Liquid is pretty disliked. Liquid received the recessive traits of his father, and that inferiority complex drives him to lead an insurrection against the US government from the frozen wastes of Shadow Moses.
But you can't just use a snow blower to find Liquid and take him out. First, he surfs a Hind-D and rains missiles on you from his helicopter perch. Survive this, and you'll eventually face him inside a far deadlier machine, Metal Gear Rex. More missiles and lasers abound. Get through that, and you'll fight mano a mano atop the burning wreckage of the mech. But three battle isn't enough for Liquid: you'll still have to gun him down from the back of a jeep as he chases you aboard a motorcycle, before finally succumbing to the FOXDIE virus.
And while that's it for Metal Gear Solid, that's still not it for Liquid. MGS2 sees his arm attached to series villain Revolver Ocelot, whose body he begins to possess. Cut to MGS4, and Ocelot has transformed into Liquid Ocelot, fully under your twin's control. But everything comes to a head in one last glorious fistfight atop the massive ship Outer Haven.
Some bosses may chase you across levels, but Liquid's vendetta against Snake stretches across multiple fights not just in one game, but over an entire series. One some level, you've gotta admire his dedication.