Master of Extras might not have been much of a fighter, but he was truly top-tier talent among Gotham's hired muscle. The key was that he was smart enough.
Though he could barely be considered a mercenary, his actual work was more like that of a bodyguard or security guard. He had worked for many bosses and faced the Bat-Family countless times.
Yet time and again, he had emerged intact from encounters with both insane bosses and the Bat-Family. At most, he got knocked unconscious or spent a few days in the hospital with minor injuries.
On one hand, it was because he did not do evil. He refused jobs involving drug or arms shipments, and he never bullied ordinary people, leaving Batwoman no reason to go hard on him.
On the other hand, he knew how to act. Many goons working for big shots wanted to put on a good show whenever they encountered Batwoman. They hoped to defeat her, get promoted and paid more, make a name for themselves, and rise to the top of the hired-muscle world.
Plenty of people thought that way, only to get thoroughly beaten by the Dark Knight and end up permanently paralyzed.
Master of Extras was different. Even if Batwoman's Cloak merely brushed against him, he would drop to the ground and stay still. He was only trying to make a living; there was no need to risk his life. Over time, he and the Bat-Family developed an understanding.
Whenever they ran into each other, he would cooperatively share whatever intelligence he had, then go lie unconscious somewhere nearby—or pretend to be unconscious. Either worked.
Even in especially heinous cases, he would at most count as the most peripheral accomplice. Fixed-term sentences and parole policies meant he would not be locked up