Complex sentence: Unfortunately for him, his carelessness with magic leads to Vicky taking over the world in the future, and now Timmy must stop her to prevent the destruction of Dimmsdale, while escaping a mysterious masked man that is trying to track him down.
Split into simpler sentences: Unfortunately for him, his carelessness with magic results in Vicky taking over the world in the future. It's all up to Timmy to stop her in attempts to prevent her from destroying Dimmsdale, while escaping a mysterious masked man that is trying to track him down.