I had a difficult father-in-law; he used to say really nasty spiteful things, and then if you reacted, he’d sneer “Can’t take a joke?”.
I eventually lost patience, called him out and banned him from a family occasion he badly wanted to attend. Mum-in-law tried to apologise for him, but I told her I’d accept nothing less and a fulsome, sincere apology from him, face to face. A few days later, he asked if he could call on me, and did apologise, very graciously. Mum-in-law said it was the first time he had apologised to anyone in the 40+ years of their marriage. After that, he was always charming and courteous to me, and I genuinely mourned his passing. He left me, by name, a precious token in his will.