A bonus character, Gat is an incarnation of the protogonist from Saints Row. With a such a lineage, you you might expect him to be overpowered, and perhaps he is, a little. His team-boosting upgrade is arguably the best in the game (boost weapon damage for all squadmates), and while his MAYHEM ability doesn't have the sturm und drang of some, its is both fun to watch and incredibly effective, particular against mobs.
If you're starting the Global Conflict missions early (as well you should be), note that, like Oni, Gat gets a bonus for missions in the starting area.