Win a tournament with each character fully customized.
You must win a total of 4 tournaments for this trophy. I just went through and changed a part of the outfit for each category on the customization screen (Hair and Headwear, Tops, Bottoms, Footwear, Accessories, and Ball Designs). I don't know if it matters, but try to make sure none of the items are part of the character's default outfit. These outfits are pictured on the game's title screen if you don't remember what they were. Note that wins in offline 2-player mode and online matches also count towards this trophy.