Ultra Sans is the final form of Sans. He can turn into Ultra Sans with his last trick. His 4th wall breaking is so huge that he can now even break the Mercy, Item, Act (probably) and Fight buttons. He can shoot lasers from his hands and head and his bones are very strong. He can even destroy the bullet board. Omega Flowey, on the other hand, can shoot a laser from his mouth and shoot nukes, pellets and triplets, so in my opinion Ultra Sans will probably win. But wait! Omega Flowey, absorbing all of the six SOULs, can use the abilities of the six humans, and can reload and make new save files, which Ultra Sans can’t do. He can also make weird hand-vines and shoot stars. He has flamethrowers that emerge from his... armpits? Yeah, that’s right. I’m not kidding.