An ultra final smash is a combination of two characters final smashes. In order to do an ultra final smash, the two characters must be on the same team. Both of there final Smash meters must be full (Yes, final Smash meters are in the game.) and they must be standing relatively close to each other. Not every combination of characters have an ultra final smash. Only certain duos that makes sense. Like Mario and Luigi, Mario and Peach, Scorpion and Subzero, Goku and Vegeta (Can’t wait to do that one!) Link and Toon Link, and so on. If you have any questions about it, feel free to ask them in the comments.