The Ex-Husband's Late Regret

The male lead was once deeply in love with the female lead, but he fell for the supporting female character's instigation, mistakenly believed the female lead was selfish and harmful, thus grew increasingly cold towards her, and eventually drove her away completely. Years later, when the male lead learned the full truth, he realized he had trusted the wrong people and wronged a good partner. It was already too late for him to make amends, leaving him with nothing but overwhelming regret.