How to instantly kill engagement with your story
In a word: contradiction.
In more words: I've read a lot, and watched a lot, and a lot of stories. I have my gripes and my grievances and my happy places. If the overall experience is strong enough I can forgive a fairly significant number of oddities because the experience in totality is so worthwhile, or the characters are so compelling, or the themes just resonate with me in a meaningful way. I can get through a lot of stories I'm not necessarily super into as long as they're entertaining enough, or there's something I can care about to take me to the end.
Usually even with a bad story, I push to the end to give it a fair shake, or at least be able to properly articulate why I'm upset. But there's one thing above all else that will cause me to tap out early, and that's contradiction.
I don't mean a character being contradictory-- humans are ridiculous, a good character should struggle with their own contradictions. Or even contradictions in the story, although if the plot hole is deep enough I will stumble into it and never get out. The kind of contradiction I'm talking about is narrative contradiction-- when you are reading something on the page, but the author is trying to convince you of something else entirely.
Have you ever watched a character who, frankly, nobody should sympathize with-- who is selfish and cruel, who always puts themselves ahead of others, who constantly makes poor decisions and blames others for their faults-- and yet the narrative treats them like a hero? Every other character is constantly comforting and bolstering them, reassuring them of how great and wonderful they are?
But you're watching the events unfold and you know better.
And it's not a case of other characters being tricked, or missing the details, no. They're present, they're watching the same as the audience, but instead of ever holding this jackass to account they just coddle them and reassure them, or even worse, try to recontextualize them as an unfettered hero.
This is narrative contradiction-- when you've written one set of events but are trying to convince the audience that the implications are something else entirely.
This is oftentimes the core of some of the most aggravating characters; people who are, frankly, terrible human beings, but who for some reason are forgiven or even rewarded for every failure while t he author tries to insist that they are in fact somebody worth rooting for. (Sometimes you even get it the other way around; a character who is blatantly doing the right thing but the narrative tries to convince you they're actually the villain.)
When you encounter this contradiction in a story, it immediately shatters an audience's immersion; they are no longer experiencing the narrative and coming to their own conclusions, they are fully aware that you, as the author, are trying to lead them to specific conclusions without having actually done the work to earn those conclusions.
I'll use an easy punching bag-- Twilight. We are told constantly that Edward is the epitome of a gentleman, straight for another time, the most gorgeous sand fascinating creature on the planet, and if you happen to think Robert Pattinson is hot I guess that works out for you. But a lot of people came away thinking that Edward was a deeply creepy (and shockingly dull) stalker, and this causes a narrative contradiction; we not only fail to get invested in the story, we chafe under the idea that it's trying to convince us to believe something against the evidence of our own eyes.
This is also why a certain type of antihero is so difficult to appreciate; the kind that regularly kills enemies, kicks puppies, sets houses on fire, but then turns around and gives you their sob story and demands your sympathy while never actually changing their ways. (The latter point is crucial; a redemption arc can make this premise work, but if you just have a character who's a right bastard but the other characters try to tell you to like him because he had a rough childhood while he himself does nothing to confront his actions is a different beast entirely. Watching somebody struggle and overcome their contradictions is compelling; watching people tell you to feel bad for a guy who clearly has no moral compunctions about his evil is something else entirely.)
One way to avoid this is to have your characters always be perfect and never wrong so any time they're glazed by the supporting cast or narrator they can't be lying. But that's its own problem.
My actual advice is twofold, depending on your needs. One thing that any story can do is just balance the conversation; some characters aren't going to like each other, or disagree with one another's decisions. This includes the good ones and the bad ones; you can absolutely have a selfish, cowardly character who somebody does try to bolster and reassure, as long as the rest of the cast treats them appropriately for their actions, and a character who does the right thing but in a way that somebody else doesn't approve of. These inter-character arguments are a natural way for people to interact. You can also make it clear that the specific relationship between two characters is inclined to function this way, as long as the narrative itself doesn't imply this is necessarily a good thing.
This is the second factor: don't use any subjective or judgmental exposition. This is much trickier if you happen to be telling a first-person story, where the narrator's perspective is bleeding directly into the prose, although you can use this to your advantage if you want to build up the narrator as unreliable or emphasize their own personal justifications in intentional contrast to the reader's awareness (just make sure you've properly communicated this intention). In a third person story, however, it's quite easy to pull back from judgmental language or exposition and just let a scene play out and leave it to the audience to come to their own conclusion.
As I said, the important part is always communicating your intent. There are few things you absolutely cannot do in any creative, and intentionally weaponizing this dissonance is certainly an option, too, as long as you can make it clear that there is an intent. But in most stories, you want to make certain that what your characters are doing is consistent with the narrative intent of what you want them to be doing.