When you're seeing a movie called Law Abiding Citizen, starring Gerard Butler doing his best "Give me back my son!!!!"-style Mel Gibson, you figure that, by the end, this eponymous citizen's convictions will be tested if not broken. His daughter was murdered, the justice system failed him, and movie conventions dictate that this means the once notably law-abiding man will now take the law into his own hands.
What you don't expect is that he'll for some reason become a makeup-less Joker, somehow pulling off ridiculously complex murder plots from the confines of a prison cell, infuriating his Batman, Jamie Foxx. Now you know to expect that:
God, this guy is a great killer! And a great crier. Really great at both killing and crying.
I wouldn't worry, though. If Jamie Foxx can't stop him, I'm confident O'Brien from Star Trek: TNG will be able to.