Thunderstrike vs Bombshell

Pretty sure Eric Masterson could take her. I don't know anything about Kevin Masterson, however.

Was that Mangog that he KO'ed?

yes,  that is Mangog.. not sure if he Ko'ed him but he gave it a hell of a shot for a kid who just came out the gate.

Is this his first appearance?

yes and no, it is his 1st mini series so yes.
but it is already in its 3rd issue i think.. so next one he'll probably find out he can fly.