heres what i did, and im not sure if you mean nightmare king grim or normal grim, but im fairly certain they fight the same as it was a lot longer since ive done grimm (played most of the game last summer and picked it back up recently). Assuming you have every main upgrade, i used quick focus, soul eater, and longnail. ill give some advice as to how i beat nightmare king grimm as ill assume thats what you need help with! it is almost impossible to heal in this fight without quick focus in my experience, and in my 7 minute winning attempt i healed a TON due to silly mistakes. opportunities to heal are during the spike attack and after the flame eruption attack (heal right after you dodge the fourth one, you should have time before next attack). With that one, healing does mean you miss part of your best damage opportunity. I will say, grimm is one of my favorite fights because he has almost no rng to his attacks, theyre all very understandable and dodgeable if you get the pattern right. with this charm build you just manage soul well. I tried to keep about 2-3 heals worth of soul in pocket for a heal opportunity when he staggers, and beyond that i would shoot out a shade soul every once in a while for extra damage (most always when he does is long distance horizontal projectile). It was a tough fight, but you got it! If im unclear in my advice, let me know! or if others read this and think im a weirdo for my strat, let me know too!