28 Mar 2019 05 Apr 2019
This is the final boss for the "immortal severance" ,"return" and "purification" endings.
As far as I know there are no cheese strategies so you have to do this the hard way.
Genichiro can be killed easily by high pressure, try to deflect his attacks and attack him as often as possible. Watch out for his mortal draw attack. It has a long windup so it is rather easy to dodge. Do not use more than 2 healing gourds for this fight. You can kill him with minimal losses, use a pellet at the start of the isshin fight, there should be enough time before he attacks you.
Now for the main fight. Isshin has 3 phases
Phase 1: In this phase Isshin only uses his sword. He has 4 main attacks and a 3 hit combo which is very slow and should always be deflected. His first attack is Ichimonji double. Sidestep and punish. Second attack is a form of the Ashina draw technique you can unlock in the Ashina style skill tree. He charges up the attack and dashes towards you to hit you twice. Simply run away quickly and run back when he did his two strikes for easy hits. The third attack is some kind of wind slash. He slashes twice, just run to the side and try to attack him quickly. He has another attack where he slashes around him in a very wide radius. You either jump over it or run far away. You should ideally finish this phase using only 1 healing gourd. If you have less than 5 gourds after this phase, restart. The randomness of the following phases forces you to have spare healing gourds.
Phase 2: This phase is super difficult. After you give him a deathblow he sends out a shockwave that knocks you away. You can run behind him if you are fast and hit him once or twice but watch out for the spear he draws out from the ground since he can damage you while doing it. He uses a spear and a sword during this phase. His reach is massive, keep your finger on block just to be safe even if you think you are far away. I have not found a way to bait his thrust attack for easy mikri counters but always keep an eye out for them. When he leaps up into the air you have two options: 1. Sidestep for a freehit or two. 2. Try to deflect but keep in mind that he does another followup attack sometimes that you also have to deflect. You can chip away at him whenever it is safe but I won't recommend it.
Play very aggressive. Keep attacking him, when he deflects you have to react fast because the wind up time on his attacks is very short. Keep an eye out for thrust attacks, counter them with mikri for massive posture damage, after mikri he will be too far away for a hit, step closer, hit him and step back again.
Phase 3: This phase seems daunting at first but it is much easier than the others. Try to memorize the wind up animation for his lightning attack. Jump into the air and hit RB at the lightning bolt and try to hit him with it for massive damage and a stun. Follow up with a hit and back off.
Thats it. There is no easy way to kill him. This fight is a true test of skill. If you absolutely can't finish it watch one of the speedrunners do it. They have a few tricks I didn't mention.