As an absolute Lingering Will beginner he can be one of the toughest bosses you may have ever encountered, especially if you are playing on critical lvl1. But once you get used to his pattern the fight can be really easy if you know how to play KH2FM. But there is always a chance that no matter how good you play that he will kill you due to lack of attention you give to the fight since he has many different attacks which will be used randomly.
Also i highly recommend using Decisive Pumpkin as keyblade since it will deal the most damage with your finisher. Also dont forget to turn off abilites such as Dodge Slash and Guard Break because that ability will most likely screw up all of your combos and make this fight harder than it actually is.