Stein is in Gotham and has been dissecting the various criminals in the city. Bruce manages to study him for a week and gets some video footage of Stein's combat capabilities. Bats then tracks him down to an old slaughterhouse just outside Gotham. Batman enters, but Stein is aware of his presence. Batman has everything he had in his belt in Arkham City. Stein has a regular scythe and a machete.
Ha, that's funny, if Batman had seen Stein's fighting capabilities then he should know better than to try and take him head on.
Stein can one-shot even without a weapon and has hypersonic reaction/combat speeds, plus is an intelligent fighter (when he's not going mad). Batman gets stomped if the only thing his prep gives him is knowledge of Stein's abilities.