My idea. 

I'm thinking of a character who was created by some type of mad-scientist or magician. 

Created for nefarious purposes to aid the mad-scientist/magicians endeavors. 

The creation was used as a weapon of evil for a long time and caused much pain and suffering to others. 

Until finally, the creation broke free from its masters hold and managed to undo all the wrong that it's master had done, taking itself and it's creator to the grave in one final heroic sacrifice. 

Cheers!