Mister Sinister used his clones to turn himself into a giant version of himself, like a poor super sentai monster knockoff. Havok proceeds to unload all of his powers and, what looks like vaporizing the giant. The cost is Havok starts to become transparent, probably like what happened to the Flash when he goes too fast using his powers.
From – Uncanny X-Men Vol. 5 #18
At first i thought you were exaggerating about the Super Sentai qualities of him, but then i saw his lack of hair in his giant form and him having more spikes and i realized you weren’t.