These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Nightmare Fuel: Kimberly's removal of her wig and the revelation of a huge, disfiguring surgical scar on her head from brain surgery. In Melrose Place's E! True Hollywood Story, Marcia Cross admitted that fans would tug at her hair to see if it were fake.
Then there's also Brooke's ghost coming back to seduce/taunt Billy, which caused him to (temporarily) turn into a Jerk Ass.
Michael visiting Kimberly in jail after she blew up the complex, and her breaking through a glass door just to stab Michael to death. (Un?)fortunately, it was All Just a Dream.
The Scrappy: Brooke is arguably the first person that comes to mind. She was so unpopular with fans, the producers had to kill her off just to appease them due to the level of hatred her character received.
Taylor is another contender. Many fans even blame her introduction for reason behind the show Jumping the Shark.
Samantha is considered this among the fandom as well, due to both her and her worthless, ex-con deadbeat father (the best example of the MALE scrappy of MP) running down Sydney at her wedding AND that fans considered her too bland and a far more boring wife for Billy, compared to the other one, who, you know, was so hated by them that the producers had to get rid of her.
Wangst: Dear Lord, Craig in season 6. On one hand, it was understandable (becoming a sudden widower, especially in such a violent way, does do that to a person), but on the other hand, the writers took it Up to Eleven and let him wallow in misery throughout the season, culminating in him being Driven to Suicide in the season's penultimate episode.
What an Idiot: The general fan reaction towards Michael after he forgave Kimberly for running him over, especially after she sent him to jail later in the season. Even worse, when he told Kimberly he knew it was her all along, what is his "punishment" for her? They began making love.