SFxTekken and P4U have comeback mechanics

It's revealed around the same time that both Street Fighter x Tekken and Persona 4: The Ultimate in Mayonaka Arena have comeback mechanics.

SFxTekken has Pandora. Pandora can be activated when your life is below 25%. In Pandora Mode, you can use EX and Super Arts infinitely for 10 seconds. If you can't win the fight before the time run out, you die. Good thing is it looks like you can't hitconfirm-Pandora like Genei-Jin. Anyway, comeback is comeback, hard or not. When you're losing, why wouldn't you activate Pandora?

For P4U, Famitsu just revealed that when your life is below around 25%, you'll enter "Awakening" mode. Your SP gauge is extended from 4 to 6 slots, with 2 slots filled. You will also be able to use the special move exclusive to this mode.