At full power he is sometimes listed as having virtually unlimited strength, and as physically stronger than Thor and Hercules, and other times as only class 90. He managed to beat the Merged Hulk by ambushing him repearedly in a sneaky manner, but Thor manhandled him pretty onesidedly after negating his force field. On the other hand, Onslaught was shown to greatly outmatch him even at its' weakest, whereas an insanely enraged Hulk physically overpowered it at its' strongest. I would personally place him below an enraged Hulk but a bit above Thor strengthvise. He relies a lot on his nearly invulnerable force field and unstoppability factor.