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.
Moral Event Horizon: Kevin Ford in Season 4, sometime after being harnessed by Marlo. Originally a suspected pedophile and questioned over the disappearance of a young boy, Marlo had followed and stalked him in her off time. However, when he is attacked by a nearby father who suspected him, Ford goes off the deep end in the Season 4 two-part finale. Having formed a hit list, he fires at officers in board daylight, and injures one officer (who may or may not have brain damage among other injuries). He captures Oliver who pleas for him not to go through with any of his plans, whilst Ford states that his father abused him when he was little and also wishing having killed a few more cops on his list. And luring most of the police station into a decoy trap into rescuing Oliver, Ford returns to the police station, dressed as a cop, with the intent of killing of one of the officers of his hit list. Though he doesn't quite shoot him, Ford shoots at and possibly kills Sam. While his backstory is justifiable, his actions of killing those involve in his arrest is not.
The Scrappy: It is not very hard not to hate the new rookie in Season 5, Duncan Moore, for being an inept rookie. And given the fact his godfather is the commissioner of the police, his job was handed to him. Then again, this may be exactly what the creators were going for...