Breaking up with a Leo can be fairly easy because all you have to do is withdraw your attention.
You start by hogging the spotlight yourself. You hog the conversation. You start criticizing. You nag. You don't remember their birthday or Valentine's day. You don't give them a gift. You simply stop putting them into the center of your life. Indeed, if you can make it clear that your concerns, your work, your career, your goals are the most important ones and theirs don't matter, the Leo person is very shortly on his or her way out. The food of life for a Leo is admiration. And once you take that away from a Leo, they start to shrivel up and leave.