Reports are coming in that a creature is taking victums into the sewers of Gotham and are never seen again. Batman investigates, but while traveling into the dark sewers he runs into the creature known as Vermin.
Well, I don't know anything about Vermin, but from what I read in his bio I think Batman could handle him. Although Vermin might be able to take him out with a swarm of rats, but gas can easily prevent that.
Batman could probably take Vermin, but he'd be in a dangerous spot in the confines of a sewer tunnel. The best bet is a combination of brains, tech and finesse, things which Vermin obviously can't match.