I'm not the one authorized to judge this, but to me it looks good apart from a few things:
- His healing ability should be a serious energy drain. Healing abilities are heavily restricted in the arena because they're counter-productive to the nature of it. If you could just heal all your wounds, there'd be no consequences to your actions.
- A general indication of how hot and how cold his combustion/freezing ability can get would be good.
Some examples for frame of reference, in case you're not so familiar, -270 C/-460 F is absolute zero, 0 C/32 F is where water freezes, 800-1000 C/1500-1800 F is the heat of common fire, 1540 C/ 2800 F is where iron liquifies.
- "speeds untraceable by the human eye" is an inaccurate estimate, as the ability of the eyes to trace something depends on the distance from the object. Either way, it's probably unreasonably high, well into the hundreds of miles per hour, probably quadruple digits. Unlike in anime, objects in real life don't simply become invisible when they go fast enough, not unless going insanely high that is.
- A more minor problem: diamond isn't all that strong. It's a common misconception. Diamond is the hardest material on earth, but the hardness makes it brittle. If you were to hit a diamond with a hammer, it would splinter into a hundred pieces. Materials like steel have a good mix of both hardness and flexibility, which is what allows them to be so strong.