Ehhh, I feel pretty mixed with this guy.
I'll go over what I like firstly. I love the HUD! I feel like at least some of it was inspired by Persona. Lastly, the spritework. I like it! Mach, uh, matches the SRB2 style very nicely.
That's all the compliments I can really give. Now for some complaints and improvements. Firstly, the character design himself. He just looks too much like Sonic for my liking. The back-facing sprite looks like an edit of the Modern Sonic v5.12 mod(not saying it is, just saying they look similar). Just kinda wish he looked more Pangolin-like and not Modern Sonic, but with The Flash's color scheme. This could be improved by shortening the spikes(?). A little nitpick, but he has several running sprites, but no running sprites for when he isn't boosting. His walking sprites look and function like running sprites, which looks weird.
Now, for the abilities. Meh, they're fine. He just feels like a more beefier Modern Sonic, just with an overheat mechanic(that punishes you by killing you, for some annoying reason). The abilities here aren't too dissimilar to any other Sonic edit on the MB. Mach really needs an ability(or abilities) that truly show off the character he is. Side-tangent, but I really wish there were more varieties with character types besides speedsters. Recent uploads have been just speed-based characters or a speed-focused ability has breaks the game.
Overall, he's a fine addition. Couldn't say too much about him since there isn't really anything outstanding about him, but I also understand that this is your first mod(ignoring the Kart mod off to the side). Things can only improve from here!