I've played that game before at my cousins' house and even beaten it, but I strangely don't know the answer to that question.
For ps2, there are no sumo slammer cards
they unlock videos and artwork
no
You have to use Cannonbolt to find all three Sumo Slammer Cards in San Francisco in Ben 10: Protector of Earth, or follow the floating Omnitrix points that will give you a Sumo Slamer Card.
If you mean the last card in area 51, you must use Wildvine to reach the sumo slammer card.
next to hamoude
byond a car
in the garden
Its in the hole by the staircase in the bottem corner in your bedroom of your grandparents house in the 5th demantion.
get all the sumo slamer cards
In the barn, you'll see 4 light thingie.. hit the 3rd switch then the 1st, then the 4th, and last the 2nd.. then the door will open.. use cannon bolt to roll up then you'll get the last sumo slammer card!!
On consoles, there's a roof you're on in one part right? On that roof, there's a big glass window that you fall through to continue the game. Use XLR8's speed to dash over it to find 1 Sumo Slammer Card. For the DS, I don't know.