Stole an ex gf gmail password when we broke up and watched how she would say things to me while she made fun of me when talking to her family. I used to spy her mailbox all the time for months to know exactly what she was doing (she talks a lot with her family). I also had a blog (mostly photos and rambling) made specifically to trick her, she was the only one who had the address and i knew when she visited (thanks to the logs) it was almost daily, sometimes two or three times a day and while having access to her gmail account i could compare IPs to know if it was her.
Than she called me back months after we broke up, officially she wanted to take some news but i knew she was thinking about me daily since i knew her whole life during the period we didn't see each other and i noticed how she would lie or omit trivial shit when we met again. Some times later i told her i had some ecstasy (we took a lot of drugs when we were together), she told me to come right away.
We took it and i hate fucked her all night long thinking about how she lied to me and how i was fucking her both metaphorically and literally. We met again some times but i had my revenge and suddenly i didn't respond to her call and just plain ignored her.
It was 15 years ago (i'm a 30+yo boomer) and it's the worse (spying, pretending like i didn't knew anything) and the best thing i've done.