it would have been a recent breakup. they were together for about a year. it was his first real relationship in a long long time and he thought he was ready to settle into something and make it work. but there were a lot of reasons for things to fall apart. he is an enforcer, for a lack of a better word, so he basically makes his living hurting people. she didn't like his work and wanted him to stop. he made a mistake back in his younger years as a government assassin that led to a young woman getting killed by the agency he worked for. he never really forgave himself and it broke him in a sense. his ex used to call it being in love with a ghost. it has caused a lot of rage in him that was only ever quelled with alcohol or hurting other people. though he has never ever been violent with her, it did lead to a lot of explosive fights between the two before she just couldn't take it anymore.