Any path that gives opponents armor up buffs makes him virtually immortal, and if the path gives other buffs too he becomes a beast. I would suggest the Ionized Armor path in 7.3.3 (starts with ghost), I LOVED that path with my 5* 5/65. The new variant also offers a good amount of paths that are really satisfying to do with VP, and the last V2 quest might be one of the best places where to have fun with him thanks to the global node which doubles buffs gained and debuffs inflicted ^_^