Oooh based on all the content, it becomes hard. I was gonna say Terry because he's the most fun for me, but if we take into account everything...
Then it goes to Joker. Persona 5 is one of my favorite game of the decade. I LOVE the stage, it's so fun. Especially like the train. The music is GOAT. And I love the character. So far, he's the one of the FP I've played the most with, even if I find Terry even more fun.
His classic mode was cool (I like all the classic mode of the FP, minus Byleth's one. But the boss of Byleth is hilarious so it's worth it just for that lol), the spirits are great since I love the cast.
So yeah Joker. With Terry being a close 2d (also 2d best stage of the FP for me, and 2d best musics)