End the story before doing endgame content for your own sake.

I made the mistake of doing almost all the endgame content (Endless Tower to stage 11-3) before going to finish the story. This made the final boss trivial as I beat him in 2 base attacks and kinda ruined the moment. So, please, in order to have a fight that lives up to the masterpiece that is the ending of this work of art, don't overlevel yourself before the final boss.

Also, on a side note, the ending left me speechless for the entirety of the credits, the writing, music, voice acting, scenery and raw emotional weight of it all just had me with only one word to react : Wow.

Also also, you can tell from just the credits how much love and passion went into this game, it's worthy of a cinematic masterpiece.