Complex sentence: Bruce manages to find a way around everything the Hand throws at him, but one thing happens that he does not expect: during the battle, Bruce is exposed to Gamma radiation that will eventually turn him back into the Hulk.
Split into simpler sentences: Bruce manages to find a way around everything the Hand throws at him, but one thing happens that he does not expect. During the battle, Bruce is exposed to Gamma radiation that will eventually turn him back into the Hulk.