'01 Hopkins would beat him straight up. '07 Pavlik's combination of size, toughness and pop would force GGG to dig deep and I'm not sure he's ever really had to do that. Also, remember that Kelly had a complete arsenal and was far more comfortable on the inside. '05 Taylor is another name that could make things interesting. He had the size and strength to force Golovkin to fight going backwards. I'm just not sure his chin would hold up...