Well, he scrambled Superboy's powers in their first encounter with gas, and used his car to weaken Wonder Girl. It wasn't quite a slugfest, and Wonder Girl was much weaker then.
If you're talking about after he died and came back, he did seem upgraded. Secret blasted him from Young Justice HQ across a forest into a mountain, and survived a double ram from WG and SB, and impaled himself to attack Impulse. Since he was dead, it seemed like his durability skyrocketed. And he had a flame blast that nearly KO'd Superboy.
He still finessed his way through SB/WG by redirecting their flight attacks and such. Never really brawled with them. The one time they landed anything, he ate dirt(snow technically).
Harm probably beats Nuke though.