I did it. Almost an hour ago I sent a large message detailing specific reasons why I was cutting myself off from them and blocked them on all social media I could think of. It was really scary doing it, but now that I have I feel so relieved to have gotten rid of them. I hope nothing comes up from this, like they find a way to get back in contact with me or something. Next I need to tell my mother that I've cut them off, which will be significantly easier than having cut said person off initially. Thank you guys for all the support.