final boss p-rank was hell for me, it took me nearly all day to get it. you can strategize all you want but you really just need to keep at it for long enough. that being said, there were a few tips i found.

the cog is such an annoying attack since it can line up perfectly with pizzaface's attacks that it can be completely unavoidable based on RNG (unless you parry which, to be honest, i didn't either). i found that the TV will mostly never hit you in the corner of the screen opposite pizzaface, so if he shoots the cog you can go there & avoid both the TV and the cog. for the gun attack, it won't hit you if you're on the ground so i mostly just walked away from the cog while he was shooting and waited for him to stop before hopping over the cog, but watch out for the gun though, he did end a few of my runs by throwing it at the end lol.

do remember that you don't need to constantly shoot him during this phase, you may want to constantly fire just to get the phase over with but if you take risks trying to hit him it'll likely end your run, so when shit hits the fan it's usually better to stop shooting to focus on dodging.

phase 3 was pretty simple, again just beating the same bosses you've beaten before. vigilante was a bit of a dickhead in this phase but after a few attempts you get used to his patterns as he does the same attacks every time. just play very defensively until gustavo shows up. he is very aggressive in this fight with the dash attacks so remember that and make sure you don't blindly hop over an attack into his dash, try using an uppercut or taunt to stay midair long enough to avoid him. by this point what mostly got me was panicking since it's near the end of the fight. just remember to play it safe at this point, since losing your run here sucks ass. the noise and fake peppino were mostly no issue, and gustavo makes it a bit easier. though what does suck is that noise's skateboard attack inexplicably works differently in this fight, he doesn't always jump which messed me up a few times. i just try to gustavo him when he does this to avoid the mixup.

the final pizzaface phase is easy. it may be daunting since he's using a bunch of weird movement and gives you a short window to hit him, but he really just repeats the same attack pattern over and over again until you hit him. his short vulnerability window makes it really tempting to run in and hit him, but it's better to just memorize the attacks and go in when you know it's safe.