In this Co-op event, players will have to defeat Wario, King Dedede, Wolf, Meta Knight, Ganondorf, and Bowser while fighting on Final Destination. Each player can be any character they choose. Each player has two stocks while each opponent has only one. Despite its name, Co-Op event 20 is not the final event. The same thing occurs in the singular events too.
- All 6 enemies in this event are rivals of the main characters in the original series. Bowser and Wario are rivals of Mario, King Dedede and Meta Knight are rivals of Kirby, Ganondorf is the rival of Link, and Wolf is the rival of Fox.
- This is the co-op variant of Event 40: The Final Battle, as both events require the player to defeat opponents who are antagonists of their universes. Additionally, Bowser, King Dedede, and Ganondorf are one of the opponents in this co-op event.