Fan Casting My God, What Have I Done? in Sort by Tropes

A well-intentioned but misguided character — very likely a Tragic Hero, a Tragic Villain or Anti-Villain — comes to realize that their actions have caused incredible damage, physical pain, emotional pain, or even loss of life. The usual line that comes after this is the title of the article (with or without the "My God"). Tears of Remorse may accompany it. Often the realization only comes when someone/something close to the person is hurt or destroyed. In quite a few cases, that "someone/something close" is the very entity they were trying to get rid of to begin with.