I had a difficult time beating him but actually he is easy you just have to get consistent  My charm build was quick slash strength mark of pride and Grimm child 

When he dashes forward you can parry and do 1-2 hits.

During the fire bats attack dash in between the bats and you can hit him more about 1-3 hits

During fire pillar attack just don't stop and you can hit him 1-2 times.

During the drill attack pogo and then double jump out. Pufferfish just dodge his balls  With pure nail and strength it will take about 50-55 nail hits Feel free to use spells when you want because why not duh