I made a cheat engine table for each character's EXP. I gave myself a 100,000,000 EXP boost for each character, which was about 50 levels in 15 minutes.
I beat Bloody Papa and Hibachi ver.2, but Centura Beast still tanks and I lost.
EDIT: Actually, the more I think about it, the more I am convinced this is a good idea in moderation. I play games to have fun. Grinding can be somewhat, but not in such mass amounts. Leveling just enough to keep it challenging sounds like a great way to finish this and not have it feel like Prison.