I'm bored and i just played bioshock again so i decided to write up a small guide to kill the final boss in the game.
Stage 1 - Fire: start by stabbing the boss(it should be obvious, he's the huge oscar award on the giant machine). Doing this will cause him to knock you off the platform and jump down himself. He will start by sending a fireball at you, catch it and toss it back at him. You will notice that this does hardly any damage and doesn't put him on fire like you would expect but you still don't want to get hit yourself. Next thing he will do is charge at you, most of the time while you are still catching the fireball. Sidestep and wrench him on the back of his head. The fire aspect is resistant to long range attacks so wrenching is pretty much the only way to kill him. Back off as soon as it looks like he's getting on his feet again. Bonus if you can cause him to charge through some trap bolts or proxy mines. If you failed to sidestep the charge or didn't get out of range fast enough after wrenching, he will start to toss you across the room and you are back at the start, exept this time you lost quite a chunk of health. Repeat.
Stage 2 - Ice: He now becomes vulnerable to plasmids but gets resistant to wrenching again. Start off by stabbing him again, and as soon as he sends youflying, grab a fuel drum and toss it at him. This will cause him to catch fire, run to the pool of water, which is a perfect place to zap him. Occasionly he will either charge you or throw a 6ft large ice shuriken at you. Sidestep the first(and let him crash into something flameable or shockable) and toss the latter at the bots. Alternatively, you can just hit the shutdown switch for the bots.
Stage 3 - ???: Once you stabbed him, grab a wrench and go splicer hunting, there's 3 leadheads, 3 thugs and a nitro. Chuck the nitro grenades at the others for some extra fun. You will notice that the boss has stopped charging you and is now tossing huge purple orbs at you that take down quite alot of health. Dodge these as best as you can and put the boss on fire(by throwing a barrel, he's resistant to plasmids now) if you need some breathing room. You can't shock him anymore so use the extra time to kill some of his friends. When the boss is back, position yourself on the corner opposite to him, as far away as possible. Keep standing there, picking up his huge balls of doom and tossing them back at him. Ocassionaly he follows directly behind an attack, in which case you sidestep him, let him take the aoe damage of his own blast and get some distance while shooting at him(crossbow if you are accurate enough). After that, keep throwing things back at him(i found it most satisfying to finish him off with the dead cat found somewhere in the room)
The final boss battle was awful for Bioshock. When I've replayed it, I always miss it out.
Awesome. Gonna try it. :)
I actually just ran circles around him, beating him with my wrench. It works rather well, if you're quick.