Fable 2 -- taste my music box!
While I loved Fable 2 and especially enjoyed the moody epilogue where you played out a day from your childhood, this was one disappointing way to take out a final boss. For an enemy that has ruined your life, fighting him with a music box is pretty anticlimactic. Still, at least afterwards you get to kill him (or let Reaver do it for you).
Street Fighter -- Every boss after Bison
Sure, I guess Sagat was okay in the first Street Fighter, if a bit overpowered. M Bison meanwhile was a tough but largely fair opponent. After that though? All downhill. Akuma appeared as a secret boss in Super Streetfighter 2 Turbo and was insanely, stupidly powerful. Gil in Streetfighter 3 was a strange blue and red striped fighter using fire and ice attacks. Rather cheaply though, his normal attacks did chip damage meaning he was insanely hard to defend against and you could almost never achieve a perfect. Added to that, he had a move which allowed him to resurrect himself from death and all his normals chained easily and did incredible damage. This led to Gil being banned in tournaments in the versions of Street Fighter where he was playable.
While Street Fighter 3 had the striped Gil, Street Fighter 4 had the all-blue Seth. Learning no lessons from their previous game, Seth was again overpowered with an Ultra combo which was brutally effective. The worst part of playing against Seth was that he would play badly for the first round, but by the final round he would suddenly use all of his most powerful multi-hit moves. Suffice it to say the multiplayer version of Seth had his health brutally gimped to make him a fair pick in tournaments. Still, not many fighting games have had better bosses than Street Fighter. Geese Howard and Azazel are just as bad.
Ocarina of time -- Its Morpha-ing time
As universally loved as Ocarina of Time is, the water temple is equally loathed. The final boss of this crushingly dull level is Morpha, a giant something. Resembling a cell with a nucleus that you attack via hookshot, Morpha is basically a big room with water you encounter at a time in the game when you never want to see water again. The mid level Mirror Link boss meanwhile was awesome, meaning Morpha is that much more disappointing in comparison.
Resistance: Fall of Man -- Man Vs Central Nuclear Fusion Reactor
What's more fun than struggling through a dull, grey, pedestrian FPS to reach the end and face a central nuclear fission reactor as a final boss? Just about anything actually. It seems that the Resistance developers (Insomniac) missed the fact that although people loved Half Life 2, not many of them were fussed with the big tower-with-a-weak-spot boss at the end. At least in Half Life 2 the tower was visually impressive. In Resistance you're in another grey room shooting at a grey pillar while being attacked by grey enemies. Grey.
Halo 2 -- Battle with a big furry
The game that promised you would take the fight to Earth has one of the all time worst endings to a commercially successful mainstream game of all time. Before this major anticlimax though, you get to fight the boss of the brutes. Jumping around like you're in Quake-world, absolutely none of what is great about Halo is present in this fight. Also, the Arbiter? Why?
Batman Arkham Asylum -- Pumped-up Joker
Arkham Asylum is a great, great game and much of what led up to this final boss fight was genre defining. That's why the final conflict with the joker on the roof is so disappointing. Set up as the ultimate schemer, the Joker seemed to have a truly nefarious, devious plan that he wanted to play out. Unfortunately, come the final fight he simply transformed himself into a giant Monster-Joker and you were left with just another standard enemy to fight. Having faced much better bosses including The Scarecrow and his brilliantly directed nightmare sequences, the final boss was just not up to the standard of the rest of the game.
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