Let me revise:
IF I knew Batman was coming for me, I would kill him with a single Beretta loaded with armor piercing rounds, Easily.
IF Batman chose to stealth my ass, that's different.
Now, for the latter scenario: If I were a Gotham city criminal, I would know Batman is out there, and that odds are that he would eventually come for me. What to do? Well, first of all, body armor. Second, I would always carry an MP5 and two Berettas, all three loaded up with armor piercing rounds, aka cop killers. Third? I would surround myself with bodyguards. While Batman engages them, I would unlaod with the MP5 (the cop killers would tear right through his armor), killing him.
It's quite simple. Batman villians, when facing Batman, are notorious idiots. I am a deadeye shot with a pistol, I would have bullets that would tear through his armor.
Do the math.