Now is the climactic final fight with Liquid Ocelot. Use R1 along with the arrow buttons to attack, L1 to block, and X + arrow buttons to dodge. The select button tells you your controls. The fight has four phases, each based on a different metal gear game. Dodging and countering is the best idea for this. Hold down L1 or else be ready to dodge at a moment's notice. Watch his attacks, and after you've blocked one of his attacks, hit him with something. Watch for reaction commands - missing these will usually hurt you a good deal. You've got a couple different attacks. Tap R1 for a combo that, if completed, will knock Liquid off of his feet. He's got a similar combo, which you need to block against. After he's done that, counter with a combo of your own.

Hold R1 to use CQC - this works best near the pillars, where you can press triangle to smack his head against them. Don't hold R1 when you get him in CQC - instead, tap the R1 button to hit the back of his head. Dash with X plus forward and hit R1 to do a body blow, which will break his guard. This is best done while he is taunting. In his second form, he'll use a powerful attack (announced with "Take this!"). Use X + back to dodge away from it, then do X + forward + R1 to do a body blow counter. In section 3, you'll start moving a lot faster, so use lots of combo attacks that lead into body blows to keep him down. Form 4 is just you guys slugging at each other. You both move really slowly, so there's not a lot of strategy.

So, in conclusion: form 1 is probably the hardest one, with a mixup of combos, heavy attacks, and body blows. Block his combos and kicks and dodge his body blows, then follow up with counters. Form 2 is a little more reliant on his heavy punch, so master the backstep-body blow combo, then go on the offensive with more body blows and combos. Form 3 dodges your heavy attacks, so use combo attacks followed up by body blows; keep an eye out for action commands. Form 4 is basically a slug-fest, so if you didn't do well in the other sections there's not much you can do here. Just mash on the R1 button before Ocelot has a chance to hit you first. Once he's down, congratulations! That's the game.

Metal Gear Solid 4 Walkthrough