What are the odds of an extremely jealous and controlling person changing?

I have the opportunity to go back to an ex boyfriend who was emotionally abusive , sometimes violent and very controlling mainly because of his insecurities and jealousy. I’ve been talking to him for almost a year to see if he’s truly changed and he seems to have gotten over those insecurities, he doesn’t express any kind of jealousy anymore and has promised me to never act in a controlling manner ever again. Is possible that he changed
What are the odds of an extremely jealous and controlling person changing?
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