Do you regret treating someone badly?

like in your immature days, you were mean to someone and they did not deserve it? especially in the love category. I liked this guy and he would pretend to like me too but then later started being mean to me and being cold/rude. I lost a lot of respect for him but I wonder if he ever feels bad? especially since we went to school together for years and had on/off flirting moments.
Do you regret treating someone badly?
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