The Red Hulk can absorb energy, mainly gamma but also cosmic, solar in particular. There seems to be no limit as to how much energy he can absorb, thus increasing his might to almost godlike levels (he seemingly killed an Elder of the Universe, and was only stopped by Galactus himself).

The Red Hulk possesses a very high level of superhuman strength, even greater than the Hulk's. But unlike the Hulk, the Red Hulk's does not increase with anger (thus the Hulk is still considered the Strongest One There Is.)