Opposite.
Have to question if you have watched the Anime
Teach and her Savior were romantically involved, but the Savior had a mentality, that special talents are gifts from God, and are meant to be used to the fullest. He helped Chisato live, so that she may kill, because that was what her talent was good for. Teach, for his part didn't want Chisato ending up a mass murderer (neither did she herself) and thus chose to use non-lethal methods. This prompted the Savior to start trying to murder her, to force her to kill (and if she ended up dying, well, she wasn't using her gift anyway, so he didn't actually care that much). To stop him for good, Teach had to put a bullet in the Savior, even after Chisato choose to spare him, since she didn't want any blood on her hands.
TLDR: Dad 1 forced to kill absentee Dad 2 to stop Dad 2 from trying to kill their daughter.