My Vote: Myrtle.
Yeah I feel sorry for Snape because he was bullied by James and all (I still want to smash James' face in with a hammer so don't be fooled), but his obsession with Lily makes him far less sympathetic especially when considering that she was never available to him but he still never took no for an answer, abused her by calling her a slur, and harassed her with multiple unwanted apologies while trying to sleep in front of The Fat Lady's Portrait until Lily comes out (ew).
Myrtle on the other hand, was bullied far more severely, we don't know how severe, but it was pretty severe due to how she described it, she was bullied for her glasses, her know-it-all personality, and her possibly Muggleborn status, all of that just to be killed by the Slytherin Basilisk at the age of 14, and yet she gets bullied more frequently just because she's a ghost and none of the girls want her in the bathroom, so she has every right to be complaining and crying, especially since she was bullied most of her life and killed gruesomely for no reason other than the Slytherin Basilisk is racist af.
Myrtle (A Muggleborn Murder Victim)
Snape (A Death Eater Who Obsessed Over Lily)