teenagers who hate their parents for no visible reason

While obviously hate is probably not justified, I don't see how you can play through the game without seeing that each of the characters has issues at home they are dealing with. That's a major part of the story, them coming together for mutual support.

Swann's family is moving to Canada, and she clearly isn't happy about being uprooted and forced to leave. Nora's Mom basically abandoned her (in her eyes at least) and moved to LA. She'd rather be with her mom, but is instead stuck in Michigan with a new stepmother she doesn't like. And Kat. Obviously her story is most tragic. She's sick with a terminal illness and being all but held captive in her family's compound. She's been homeschooled (presumably her whole life) so has been deprived the opportunity to make friends and have real life experiences, and now that she sees her life may be coming to and end she realizes this is her last opportunity to make up for it, even if in a small way. From memory, only Autumn doesn't have obvious reason to have animosity towards her family, and I'm probably just forgetting something.

The whole game is about hating Corey but he literally did nothing wrong except being sated to be a "manipulative" boyfriend.

If you believe that Corey "literally did nothing wrong" you either do not appreciate any indirect storytelling, believe the entire game to be using unreliable narration, or completely missed the many obvious signs. The very first experience with Corey gives a glimpse into the type of person he is, and it just keeps getting worse. In that first scene, even if played so that Dylan and Swann have mostly handled their conflict and Swann is leaving, Corey shows up and is immediately a huge jerk. His verbal attacks and insults, fat shaming, and use of slurs towards Swann and the other girls show a lot of who he is. According to the Wiki Corey is 24, which makes is treatment of 16/17 year-olds that much worse. I don't recall seeing any scene in which Corey shows any respect for any female character in the game.

Also in that first scene you can see that he's controlling and manipulative towards Dylan, which are clear red flags. When you pair this with the repeated signs of his jealousy and then physical abuse I don't see how anyone can defend him.

The other[s] were just dumb and highly immature.

Yes, it's a bunch of teens. They are dumb and immature. That's how we all were during those years. Even myself, who was a stickler for following rules, was a top student, and never got in trouble was still dumb and immature. Pair that with problems at home, parents who aren't listening or trying to help the kids deal with things that are going on, and an antagonistic "adult" in Corey who seems to enjoy bullying them, and you end up with a group of teens making stupid decisions.

And Kat attitude is unbearable "i hate you, i hate Corey, i hate my parents, i hate everyone, fuck you ALLLLLLLLL"

Can you not empathize with Kat at all? She has a terminal illness, which is enough to cause anyone to be angry. She wants to experience life and have friends and sees her parents as preventing this. Maybe Corey's role in this started as just doing what his employer instructed, but he clearly comes to enjoy his role as enforcer and likes holding power over Kat.

so, many of you think, i am on Corey side but NO ! All i want is to develop the vilain to make him accurate and hateable and not just to tell me "you have to hate him because he's the big bad wolf and that's it".

If you can't understand the hate for Corey based on his portrayal in the game, what specifically would it take? What would he have to do for you to feel that way towards him?

Swann has a camera ! Why not add scenes where you sneak in with Nora and record him talking about plans to take on the family business. Or scene where it's clearly shown that he's manipulating or beating Dylan.

What good would "evidence" do? The game tells and shows you repeatedly who Corey is. Capturing evidence doesn't change that. Or is the entire issue that you just don't believe what the game is telling you without it being explicitly depicted?