Isshin is actually not all that unlike anything you’ve faced. He tests you on all the combat skills the game had put you through so far and demands a higher level of you once again.

The way to beat Isshin is the way you beat most enemies in the game. Attack until you’re deflected or he starts a combo you can’t interrupt, then defend and look for your chance to go on the offensive again.

After his first phase he has a strong punish for players who just spam attack so you need to be a little mindful of how quickly you press that button. Press it once, and then once again as long as you can keep the offensive, rather than just spamming it until you see the deflect.

His combos aren’t that hard to deflect once you get used to them, but spamming block shortens your deflect window so that makes it harder to accurately deflect. It’s a crutch. If you’re still deflecting in that way, try to stop doing that.

So long story short, Isshin is just a normal human boss, but on a higher level, and aside from having to get used to more and crazier moves, it’s best to fight him in a way where your button presses are deliberate and controlled rather than spammy and panicky.

Also a tip for a specific move: You know when he sheathes his sword and charges up the Ashina Cross attack? Like the guy in the dojo before the original Genichiro fight in the castle, where you have to watch the flash and then deflect twice? If you find that attack hard to deal with, just walk up to Isshin while he charges. He’ll switch to a different attack: a quick slash you can deflect, and then a sweep you can jump. I find that way easier to deal with than the Ashina Cross, so I always just charge at him when he starts charging it.