I'll start.
My Ex partner (many, many years ago, long before mobile phones/home computers etc) was handsome, successful, ambitious and seemed lovely initially. As time went on, he used to deliberately exclude me from social events, and invent excuses about why I wasn't there to friends.
E.g He'd already have left for a night out (that we were both invited to and expected) before I got home from work. He'd have deliberately not told me the where and when we were meeting the others by evading my questions about it, saying things like 'you just need to remember to be ready to leave by 7pm' so I couldn't even join them later.
This happened whenever he was the one who had had the invite conversation or phone call, and it didn't even matter if it was my friends or his who had invited us! He used to tell our friends that I was 'working late' or 'too tired' to come!
The one that 'broke the camels back' so to speak, was when we were on New Zealand (he was a kiwi, and I was to stay there on a 3 months no working visa). We had spend several months travelling together as planned(Iceland, Greenland, Canada, USA etc)
After we'd been there (his hometown) for 6 weeks, both splitting the cost of rent and a car, my savings were running low, and I told him I'd need to leave sooner than planned because of this. (He had already found a well paid job.)
So he said 'I'll cover the rent/bills so you can stay', but what he meant was 'I'll pay for my house and car, and you can serve me like a king and keep my house, cook my meals, do my washing etc , but I was to remain at home at all times !
Meanwhile HE went out every evening and weekend with his friends, leaving me in a remote area with zero public transport with a 10k walk to the nearest feckkin shop ! And he told all his friends that I wasn't very 'sociable' and didn't want to meet them !
I raised the subject almost daily, to no avail. He didn't see a problem with him physically isolating me from all human contact except him!
So I finally got him to drive me to the city, and I DID book a return flight to the UK asap and told him I was leaving, and he had the feckkin brass neck to say 'Why are you going? Weren't you enjoying being in NZ?' and 'What'll I do without you?'
Even once I was back in UK, he wrote me a long, self pitying airmail letter saying how much my 'abandoning him' upset him, (He cried at the airport) and did I know how much he 'needed' me?
Apparently, even me leaving him to travel half way round the world wasn't me actually ending our 'relationship', he thought we were still 'together' ffs !