Oliver and the others were shooting at Hektor who was now using a similar strategy to Richter's. Basically, he was blocking all the attacks that were aimed at his head, and he doesn't bother with everything else. With the nanomachines, all attacks that don't detach his body parts, and were not aimed at the head were almost ineffective. It was like they were fighting an immortal fighter.
Hektor was also having fun as he pounded away at Oliver, Niel, and Sayaka. Though it wasn't really a one-sided fight, seeing as all of Hektor's wounds were healing while the members of the Mercenary Club retained their injuries, it looked like a one-sided fight.
Hektor's damage was only some bullet holes in his pants and a bit of his uniform, but no real damage to his body. On the other hand, the Mercenary Club members had numerous bruises here and there.