Not totally sure if this counts, as I actually still love her and she's a wonderful grandma to my son (they are the apple of each other's eyes, honestly) but still. My boyfriend's mom.
Outwardly she is polite, proper, kind, etc. She's also and ultra-conservative, Disney-movies-are-Satanic Christian, which is honestly fine for the most part. Boyfriend was raised that way (we're both liberal Christian-ish now), and I don't care much what your beliefs are as long as I'm not getting harped on for them. She does like to give me a hard time about being pro-choice by throwing the fact that "her whole family wanted her to abort my boyfriend and aren't I glad when I look at my son that she didn't?!"; apparently forgetting that she told me years and years ago that she DID have an abortion and that my boyfriend was a miracle baby she prayed for years to have… she's just pretending it was him that her family wanted her to terminate to have something to throw at me.
Anyways, the thing that really got me past being an utter pushover with her (which is my meek, doormat-ish version of "disliking" someone) was her recent re-engagement to the man who abused my boyfriend when he was little. They were married when bf was 9 or so after the stepdad who'd raised and adopted him died, and divorced shortly after we started dating when he was 18. He has burn marks on his arms from lighters, was once grounded to his room without books or TV or anything for a year, and frequently has his things sold to support his step-dad's drug habits. The guy was mentally and physically abusive to both of them, eventually his older brother took their mom to court for custody when bf was 16. His mom's family essentially disowned him for "causing her so much pain."
They all eventually made up, but about 3 years ago Stepdad came back into MIL's life. She decided G-d wanted them back together since they were still married in His eyes. Stepdad has MS and is now in a wheelchair, so she told bf that since he's not a physical threat he should be able to get over it and forgive the man. We agreed to go to the wedding, which Stepdad kept pushing back. "If you do THIS, we'll get married." So she would do the thing, and he'd have another condition. Rinse and repeat. He pretty clearly wasn't interested in getting married, but it's her life and G-d wanted her to, so whatevs. After a few weeks Stepdad said something about how my boyfriend needed to grow up (it was over some stupid joke his mom seriously overreacted to, but this story is already long) and boyfriend snarkily said something about it not involving him. He called off the wedding, and MIL immediately decided it was my boyfriend's fault. She didn't speak to him for a while, and then she started guilt tripping him about how he needs to go apologize because G-d preaches forgiveness and he's not being Christian. Now, my faith is shaky at the best of times but boyfriend's is pretty important to him. He listened for weeks while she questioned his faith, his love for her, why is he being so unreasonable, etc. The whole wedding falling apart was HIS fault but anyone else could see stepdad had been looking for an out way before the stupid, mild fb rebuke.
TLDR (Sorry I know I'm long-winded): Boyfriend's mom divorced abusive stepdad, then demanded boyfriend forgive him before their remarriage, then blamed boyfriend when it fell apart for not being nice enough to him.