Round 1 is hard because Grundy doesn't have a normal level, sometimes Batman can floor him, and one time he came back strong enough to whoop everyone in the JLA. His level fluctuates so much that it's impossible to say he has a normal one.
Round 2 is Grundy, because at his beast he ko'd Superman with less than 6 hits, and Ultimate Thor is far weaker than 616.
Ultimate Thor just isn't up to par with full powered Grundy, either mindless rage Grundy or super smart Grundy could rip Ultimate Thor apart with no problems. And like I said, the regular limit on Grundy just doesn't apply, because once he's come back and been cut by batarangs, and punched out by Bat's himself. Another time he came back and a full powered punch from Superman didn't even register.