Welp, technically it's not character design because you did not design the character, you simply drew your RF character.
As Daril said, this isn't character design since you didn't create anything on the character, you just drew your Rumble Fighter character. Also, some constructive criticism - The fingers on his legs are strangely arranged, in most cases the middle finger is the longest and in rare cases the thumb finger is the biggest one, it's kinda disturbing how all of the fingers on his feet are all the exact same lenght. 2nd, don't use paint to draw this kind of stuff, the brush is extremely rough and the art doesn't look as clean. I myself am an artist and go to an art school so I think I understand some stuff. Wanted to open up a shop for chibi characters since people demand them alot but I decided it's too much work for in-game items of a game I don't even play that much. Also, his feet are mismatched in size. The left foot is bigger than the right one for some reason.
Made a mistake, it's the thumb finger that's usually the longest one on feet and in rare cases it's the middle finger.