Arthur Fleck is not a strong man. He shares the same mentality as most high-profile serial killers and school shooters: weakness. People like this may agree with me that the world is horrible and unfair, but they crumble under the pressure of these thoughts. They get lost in the despair and hopelessness of this notion. For some reason, all of these people one day decide that they should take on the role of God, casting judgment and sentencing. They should deliver justice with their own hands. They are responsible for punishing those that caused their despair. They decide that you get what you deserve. What a terrifying thought.