This is a movie I watched probably seven or eight years ago, and it looked pretty new back then. Early 2000's I'd say. Here's what I remember:
- It was in Chinese or Korean
- Also set in either a near-future dystopian China or Korea
- The protagonist was a young woman
- She is convicted of something and sent to prison. I'm pretty sure she was innocent.
- While in prison she kills another inmate by rubbing butter on the floor near the pool
- When she gets out she builds a special gun that she designed using multiple over-lapping sheets of paper (the blueprint was displayed when all the sheets were held to a light)
- The gun looked like a steampunk pistol but fired like a shotgun. I think it was only used once and it missed.
- Movie ends with the torture of the woman's sex offender. There were lots of other people there as well who were or knew the offender's other victims and wanted revenge.