Splatterhouse

Story Achievement, unmissable. This boss has 3 phases.
Phase 1: Like the other bosses, the key is to learn his attacks. Be aware his exhale after his slam attack does damage you. Watch his method of attack, launch your counterattacks when you can, and you will enter an interactive cutscene where you jam one of his rods into his head.
Phase 2: Phase 2 is similar to Phase 1 except he has 2 new attacks. Otherwise, keep avoiding his attacks and jumping over his AoE slam while launching counterattacks, and you will once again enter an interactive cutscene where you rip one of the rods from him.
Phase 3: This phase plays just like Phase 2, but you have a weapon now. Your attacks will be more damaging, making this a significant bit shorter than the second phase. At the end of the phase, you are once again prompted to grab him, which ends in a cutscene.

In the final battle of this stage, you have the honor of fighting a large robotic ape. If you read the solution above me, you'll notice what happens in each phase, but this doesn't exactly help you beat the boss at hand.

If you're having trouble, I recommend trying this. Firstly, don't even bother trying to dodge him as he tries to swing at you. Instead, continuously ram him (RT + Y). If he's charging you, you never take any damage, and he tends to miss you most the time while you're charging and he's swinging at you. Ramming him is the quickest way to build your splatter bar as well so as soon as you've built 3 bars. Activate it and hack away with immense power and invincibility. Don't tap out X to the point of making Rick perform a full combo. Just perform single slices as they are very powerful and less time wasting when he misses the final X-Scissor cut :) Still dodge his shockwaves though. But apart from that. This is now a cake walk.

Don't forget that after each phase the game saves a checkpoint. Have fun ramming :)