My sister let me move in with her when I'd just gotten a new job in her area. It was like a mature-age apprenticeship, shitty hospitality hours most days with one day a week of school. I paid rent, babysat the kids when I could and accumulated savings whilst trying to stay out of the way as much as possible. My sister was heavily pregnant and it was a difficult pregnancy, so she spent a lot of time just lying down. I tried to help with housework and stuff with the kids so I could be more of a help than a hindrance (they're my niece and nephews so I love them anyway). But her boyfriend was the scumbag kind of junkie so it was never going to work.
First red flag was a piece of jewellery that went missing. He was dropping all these hints till I said, "If you're going to accuse me of something, come right out and say it." My sister knew he had hocked it but because I've been in prison her boyfriend thought he could plant these seeds in my sister's head. I've never been accused or convicted of stealing anything from anyone.
Next he offered to drive me to work one day. Seemed ok. On the way he told me how his car needed urgent work or my niece and nephew would be in danger being driven to school. I told him I had no money on me, which was true. He asked about my savings and my heart sank but I felt kind of trapped. He promised he'd give it back within the week and only needed $70. I came back from work to find that not only had he taken $800 - he was also denying it. Thankfully my sister knew there was no other way he could have found where my savings was hidden. He had a tantrum about giving it back and actually said, "Do you expect me to go rob some little old lady for it like you would?" I don't even know where the fuck that came from but in the end he stole the money to pay me back from his own elderly mother so maybe he was dealing with pre-cunt-act guilt.
So my sister then took on the job on holding on to my savings. Got to the point where she had to keep it inside her pillow while she slept. He cut her face trying to get to it one night while she was asleep. Another time I wasn't supposed to finish work until about 1am but a function was cancelled so I came back just before the kids were due home from school. They would always go straight into the old dining room to watch cartoons and colour in on the big table. I walked in to that room to find uncapped syringes, dirty spoons and bloody swabs all over the table. Knowing the kids were due any minute, I carefully packaged it all up and put it in a high cupboard in the kitchen with a note on the outside saying where I'd found it and when. He called the next morning assuming my sister to be livid with me for leaving drug shit laying around. Turned out she was pissed at him.
By this point I fucking hated this guy. He was also epileptic and when he had a seizure he had no memory of just before and just after. A few times I had sat with him or given him a pillow so he didn't hit his head. A knock on the head could bring on a seizure. One day I was starching my chef whites in the kitchen and I guess some starch accidentally got on the floor. He charged into the kitchen screaming at me to give him money (again), slipped and bumped his head on a cupboard. A few minutes later he started seizing. I was supposed to watch him and put a pillow down so his head didn't bash on the cupboard. By this stage I just walked outside and laughed while his head kept bashing the cupboard. I didn't feel bad. Later him and my sister thanked me for watching him.
It all came to a head one night when my sister called me at work frantic. She was very heavily pregnant and sick and he'd knocked her to the floor screaming at her to hand over money. When she refused, he held a used syringe to my 10 year old niece's throat (she was in bed asleep at the time but still, for fuck's sake). At least, that's what my sister told me and I had no reason to doubt her.None of the kids were his.
I told her for the hundredth time how I didn't want to get involved as they'd both just end up turning on me when they kissed and made up. She insisted it wasn't like that, that she was serious this time and afraid and just wanted him gone. We're from a cop-wary family so she didn't want to call them. She wanted me to physically remove him. I went back and he wasn't there. He was watching the house from his car outside. I went and asked him to leave, he refused and pulled a knife. Big tough guy pulling a knife on his girlfriend's little sister. Well, I didn't go to gaol for stealing...
Long story short I took the knife off him and got him on the ground pleading for mercy and screaming about calling the cops. My sister came out and asked me to release him and they kissed and made up. I took my savings and spent the night on the street before booking in to a shitty, feral, overpriced dive motel. Luckily a mate of mine had someone move out a week later and offered me a room there.
TL;DR - Doing the right thing doesn't always help. Some people are just cunts.