After absorbing 3000 percent over his limit of solar energy sunspot is about to explode but shielded by his blast shield cannonball is unharmed x-force #15.
Cannonball did great against Gladiator, considering how much faster, stronger, and generally more powerful Gladiator is than Sam. That alone is worthy of respect.
However, Sam never "defeated" Gladiator. He gave him one good hit and then the X-Men showed up (which was Gladiator's goal) so the fight was pointless.
Look at that last scan. Does Gladiator look "defeated" to you?