A stroke of luck made "Mad Dog" famous.
Now, in Baghdad, nobody dares to mess with Gao Guang, and that's because Hank was single-mindedly pursuing military achievements. He led the air and ground forces in a bombardment, slaughtering chickens with a bull's knife to show the monkeys, which established his boss status. One could say Gao Guang benefited from the circumstances by mere coincidence.
But the status of a boss is somewhat tenuous, yet this reputation for being a fighter was solidly earned with true skill.
The Tiger Mercenary Group was Gao Guang's stepping stone, and Ottolov was the noble benefactor that helped Gao Guang make a name for himself in Baghdad.
Logically speaking, mercenaries wouldn't easily seek revenge, because fighting is just a part of the job for mercenaries. Killing and death are just too commonplace if every death called for vengeance, then after fighting a couple of battles, the mercenary group would do nothing else but run around seeking retribution.