Deoxys
Not every character needs to just stay the same; they ought to be able to transform at will as well. Deoxys is perfect for this, similar to Shulk in Super Smash Bros. for Wii U & 3DS. Both of them can switch between various forms that allow them to alter their stats on a whim, to focus on various attributes such as speed, defense, or attack.
It’d be pretty awesome to see Deoxys switching between its four forms as the situation calls for it. Perhaps it needs to escape and give opponents the runaround, so the Speed form would be perfectly handy. Maybe Deoxys is getting beaten pretty badly and need just a few more seconds to think up a strategy, the Defense form would be perfect to hang in there. Or perhaps the player just wants to add some insult to injury and really make those finishing blows that much more powerful, in which case the Attack form is just the ticket.
Differing strategies require differing forms, and Deoxys would be able to fit right in with the rest of the wacky roster of characters. A great fighting game has plenty of different tactics for each player to choose from, after all.
