To combine two that I've seen in this thread to make sense and avoid confusion with acronyms, Super Smash Bros. Battle Royale. And one of the single player modes would have to be called Battle Royale, where you pick one character and try to defeat every other character in a specially designed stage for the battle, and you can't escape to a different stage or an in-between stage to rest and heal up if you need to. Plus it starts off just you and one random opponent and you have a countdown timer of five minutes. Instead of the tradition "Fight Over" countdown timer, when the timer runs out, a new opponent spawns and the timer resets until either you get killed, the stage is filled with the max number of characters, or the last opponent spawns. Both this mode and All Star mode would be unlocked when you unlock every character in the game.