Lovesick Trials Relationships: Killers
Most killers will typically go after the survivors that came from their respective world or, if they have multiple, the ones they are typically associated with: Michael and Laurie, Trickster and Yun-Jin Lee, etc. As there is usually some sort of connection between the killer and survivor that makes it easier for The Entity to manipulate the killer's feeling towards the survivor.
This is especially true with killers like Pyramid Head, Wesker and Michael Myers for example, as those three would only go after the survivors from their respective worlds for different reasons.
Pyramid Head pursues James Sunderland due to the very nature of it's existence is being his punisher, this can go many ways as The Entity can alter the parameters of the punishment to a degree.
Albert Wesker only has fixation with the former S.T.A.R.S agents and the people who got in the way of his plans back in their universe Leon, Claire, Ada and Sheva. So he just wouldn't care for the other survivors, believing them to be unworthy of his attention and energy outside of the mandatory tasks of the trials.
Michael Myers is already canonically obsessed with Laurie Strode because she is either his sister or 'the one that got away', except this obsession is a little less murderous than it is in canon.
On the other hand, not all killer obsessions are set in stone, variations can occur depending on the lore of a character and whether or not they have a set survivor.
For instance, the Huntress's obsession would alternate between survivors like Cheryl, Nancy, Mikaela, etc. Basically anyone who could fit in with her lore of kidnapping young girls because she wants to raise a little one herself. Meaning that most of her yandere relationships would typically fall into a platonic/familial catagory.
Another would be how the original four killers (Trapper, Nurse, Wratih, Hillbilly) would alternate or share the original four survivors (Dwight Fairfield, Meg Thomas, Claudette Moral, Jake Park) due to how long they have known each other within The Entity's realm. While they could go after the different survivors and other killers are allowed to go after the Dwight and the gang, but they typically gravitate towards the four that have been with them the longest in the Fog.
Alternating obsessions also decreases the chance of 2 vs 8 trials as The Entity has to be careful on who gets paired up as it is possible that a survivor can get multiple yanderes at a time. Which doesn't last long due to the amount of infighting it could cause over an extended period of time and the fact that The Entity also wants to have at least one yandere per survivor. So no one is safe from being so adored? and loved, surely that is a better alternative to being killed all the time isn't it?