Hearns should beat him, unless he, Hearns, gets chinned... Nunn could & most probably would. But Froch would be the best fight, where many might favour GGG, however I think the toughness & durability of both make it 50/50. Pavlik has little chance.
Absolute best Golovkin would probably beat them all. Nothing is certain though because that's a high level list of fighters right there.
Hearns is the only issue. Thomas is certainly capable of outboxing him if he sticks to his game plan so I'll run with that. He beats all the others.
If Hearns fights him the way he did Hagler, Hearns gets starched. GGG beats the rest, Froch is likely his toughest fight.