So many things.
When my waters broke with my ds I wanted to get changed and my ex told me to stay in those clothes as I would, no doubt, be milking it and he would be doing the washing, so I had to walk about in wet clothes for hours.
He also told me after dd was born (My son had died years previously, and my other daughter had died the year before) that "Karma was probably going to kill this baby too" because I was such a cunt, then started laughing saying "who even has two kids die on them". (Dd was his, ds wasn't).
When he and I split up he and my mother joined forces to try and get my dc taken away, they were calling the health visitor and social services every week saying I was calling my dc by my dead children's names, beating them etc as my mother wanted custody 
Years later my (then) partner of 3 years and I had a baby, my other dc were with their auntie and my dd was 2 days old. This probably sounds funny but it was fucking horrible. I was sitting with my new baby and all of a sudden this news report came on the TV, breaking news about a nuclear bomb, it was so bloody realistic, videos of the PM getting whisked away, footage of various things, then it was announced that a bomb had been launched at the UK. I felt fucking sick, I was trying desperately to try and get in touch with my sister to get my kids, and I couldn't reach her. All of a sudden my ex started laughing his head off, and told me it was a joke, it was a YouTube video. I cried for days, it was one of the worst things anyone has ever done to me
ill never forget that feeling.