Not my last relationship but with a girl I dated in college. There were red flags I had ignored. She would get upset with me if I didn't do exactly what she wanted, when she wanted, regardless of what I had going on. Say I couldn't meet up because I had work, or if there was a time I wasn't in the mood for sex (mind you we didn't have a dead beadroom). She had a huge drinking problem, would frequently get wasted and throw a fit at the drop of a hat, or want me to come from wherever I was for sex (she was so inebriated I knew it would be wrong and would generally take care of her and have her pass out in my bed with nothing happening).
I had been having doubts about things but was holding out in hopes that the person I fell for would resurface. Recruitment for her sorority came around and she prioritized that over me, I had taken some extra time over winter break with my family due to my dad's health and she was giving me shit for it because I wasn't there for the odd hours when she wasn't with her sorority. Shortly after that, I was incredibly sick, like on an IV of DayQuil, stay in bed all day, no appetite, watch Netflix and play video games all day sick. She was pissed at me for wanting to lay low for a few days and still expected me to pick her up from her sorority parties late night. It was at this point that I began to realize she didn't really care about me if she couldn't get her way with me. She would throw the phrase "you don't love me" at me all the time as a way to gaslight me. Anytime I would call her out on these things and try and talk about it with her and how I felt, she would flip the script and play the victim. There was also a night where I picked her up from one of her sorority parties (I wasn't in Greek life at that time, so I couldn't go to the mixers her sorority had) and we had a conversation that led me to believe she cheated on me, trying to get a rise out of me. I had no proof but the idea would not leave my head.
Eventually, the post-college conversation came up and as we were talking all of these things kind of hit me at once and the glass shattered. I realized that I was with a person that didn't care about how I felt or what I wanted. I know I'm not perfect, there were communication issues, I was learning, but I tried my best to make her happy and enjoy life with her. A healthy relationship is built upon trust and supporting each other, and I definitely didn't feel those things. What ensued was the nastiest breakup I've ever had, with her saying and doing everything she could to get me back, including threatening to kill herself. I knew it was likely one of her games but I wasn't taking any chance. I told her roommates about it and went no contact. She tried to flip the script and paint me red, but her roommates knew me and they saw right through it. She was trying everything she could to get me back because I was no longer validating her in the way she wanted. Her (eight) roommates all told me they were on my side of the breakup and I had put up with so much shit, that was when I knew I made the right choice and realized just how toxic of a relationship I had been in.
Months later we tried to be friends but she just wanted to hookup and gloat to me about her life, like she was trying to say I was missing out. She was an incredibly narcissistic, insecure person that seriously needed help with her problems. I hope she has found or will find that help, but she has no place in my life and I wish her only the best. I learned a lot from that relationship, especially what to watch out for and what I deserve.