from what I remember, Genevieve and Danneel got it the worst. Jensen supposedly brought Danneel to a convention once and Danneel got heckled and threatened so bad that he didn't want to do conventions in that city anymore. Genevieve got a lot of threats starting when her character was only involved with Jared's character, so I bet when they got married it got even worse.
the most I've seen fans say about Victoria is calling her ugly which is ironic considering what the fans look like. I guess because Misha Collins plays along with the fans' bullshit they think they have a chance with him.
speaking of Misha Collins, that reminds me of another disturbing part of the Supernatural fandom. years ago he starred in a movie called "Karla," which was a biopic about Paul Bernardo and his wife Karla Holmolka, two serial rapists and killers from Canada. when the movie was being made, there was a HUGE uproar in Canada since the rapes and murders were being acted out in explicit detail and the case haunted Canada. Collins happened to play Bernardo. I've seen the movie. it's really disturbing and paints Holmolka in a positive light. very unsettling movie.
once the fandom found this movie, they turned it into a fantasy for them, thinking it was sexy and funny and would make jokes to Misha at conventions despite him flat out saying he was ashamed of his part in the film and urging people NOT to watch it. he even said he and Laura Prepon, who played Karla, got a restraining order against the director because of the way the director acted, which was similar to how the fans reacted to the movie (calling it hot, sexy, funny, etc when the cast was crying after filming a scene). the fandom makes gifs of the rape scenes and fanvideos, they think it's great and hilarious even though Collins himself has asked them to stop. I have no idea why he still interacts with them when they are so disrespectful to him .