JUMP FORCE

This is basically the next level compared to get the other cheevo clear an easy mission. Now I would say the best course of action would be to complete the storyline as you will face all levels including at the very end an expert like boss.

Characters I would advise using
Go with the first one the character you are most comfortable with, me I use my custom character

Next go with a sword character, they are considered the best in the game with 5 out of the top 10 overall characters being sword characters. go with either Aizen, Roronora Zoro or Asta

And now you want either a buff character or ranged one, great ones to consider are Killua, Hishoka or Freiza

Self-explanatory - Clear any Free Mission on Normal Difficulty at any Rank