I have so many evil thoughts towards their child

Good day house, please I need your help on how to handle this. I used to date this gut about 7 years ago and he was very mean to me, he used to beat me and insult me, there was a time he poured mud water on my body just because I told him I didn't like that he wasn't taking care of me like other boys do to their girlfriends. This was 7 years ago, I was just 17, I was still very childish then and he was 25, I expected him to understand better. Now, it's been 5 years since I broke up with him, we are both married to different people. My husband and I just moved to our house in Ikorodu and we joined a new church, the church we joined happens to be the church my ex and his wife attends. I am a chidren's church teacher and his daughter is in my class. Every time I see her, I just always remember how her father humiliated me while I was with him, I always feel like beating her back, so most times I just make her feel like she is not doing well in the class even when she is but I still always feel like I am not hard on her enough. Her father has never said sorry for all his misdeeds, he always acts like he doesn't know and I want him to beg. I have so many evil thoughts towards their child, please mamas, what should I do?