I've not been stalked, but I think someone I knew may have had the potential. We'd spoke for a year or more. She developed an interest in me, but I didn't feel the same. Then I entered into a relationship with a different woman and ended up moving to be closer. So I told the original woman I didn't feel comfortable staying friends with her, while in a relationship. Especially since I was moving to the same state she was in.
She spent over a year writing letters to my dad asking him to send them to me, hoping I'd get in contact with her. When I found out I was pretty creeped out. Fortunately it never went further.
But back then I did know two other women who had been stalked. One of them twice. The one that was stalked twice, by different men, years apart, was fortunate that each man was caught and arrested before any violence happened against them.
The second, however, was cornered and had her arm cut with a large knife.
She knew someone with a very bad past. And her stalked was discovered having "killed himself" with blood splattered all over the room...
Scary stuff indeed.