My system with RHGs is that they should have a primary ability- yours being speed- and a secondary ability, with a possible physical enhancement like armour or buffness.
Your guy is just fast, really. Why not make him like, unbelievably fast? Almost all RHGs have fast as a secondary sort of ability, but why not just have your guy be 100x faster than that?
Here's an idea for you. He can run up to mach 5. If he reaches the speed of sound (mach 1), out comes a shockwave. If he reaches mach 2, the air friction causes him to become a running ball of flame, the fire not hurting him at all. Mach 3, he ditches the fire and becomes so fast that he's practically invisible to the human eye and the world around him seems to slow down. Up to mach 5, he's casually running in a world where time has stopped.
The balance to this would be that he'd need a lot of room to run this fast. All characters are pretty OP, and your guy is too generic to really compete with that. Don't just make speed a secondary thing, man. Turn it into a beastly weapon.