I would actually posit that Kylo Ren is one of the worst characters in Star Wars history, as well as the uncontested candidate for the one I hate. Some may scoff, arguing that characters like Vice Admiral Holdo or Rose Tico are patently worse, but I would disagree.
Kylo Ren, to me, embodies all of the ST's worst problems. He's an aimless, underwritten character whose edgy animu conflict is shouted at the audience through maudlin exposition instead of being shown to them, and whose motives are practically non-existent. Ancillary writers for the comics and novels have had to write mountains of material to explain this character because his on-screen incarnation is so shallowly-written and paper-thin, that we as viewers have virtually no idea what drives this character, or what supposed "trauma" he's been through. It's as if the writers just expect us to care about him simply because of him being the offspring of characters we care about, and they can simply ride on that investment without having to try hard to write him well. As a result, this character lives and dies on whatever feeble exposition is thrown about him feeling isolated and alone, and Adam Driver quivering his lip like a constipated child at regular intervals. All of his struggle exists off-screen, through things that have happened to him that we didn't witness. Snoke manipulating him through the womb, being neglected by his parents, being the troubled student at Luke's academy...we aren't shown any of this, and yet we're inexplicably expected to care because we're told about it. It's telling instead of showing of the worst kind, implemented to the character whose redemption is the supposed emotional focal point of this new trilogy from the beginning, instead of being a surprise late-game goal like Vader's.
And this wouldn't piss me off as much if the story didn't bend itself five ways to Sunday trying to not only get the audience to feel sorry for him, but justify him as some kind of fucking victim. These writers want me to feel sorry for some emotionally-turbulent manbaby, who throws a diaper-shitting tantrum if someone so much as looks at him funny. And not content with framing the trilogy's tragic undercurrent around this insufferable cunt, they actually wrote the OT Heroes completely out-of-character in order to narratively accommodate him. Han and Leia are suddenly awful parents, with Leia being a business-first workaholic and Han being a neglectful asshole who walks out at the first sign of trouble and regressing back to his selfish smuggler self. And Luke? Well, he exercises the restraint, patience and understanding to work and train with every other student at his Academy, but when he has trouble with Crylo and senses a potential vision of what he might do, he relapses into the impulsive idiot he was during ESB, the kid who reacts to visions too quickly and acts without thinking....all to absolve little baby Kylo of any blame, and make his actions and Dark Side Turn the fault of other people.
Now, I'm not married to the OT or its characters like a lot of other people are, but I know fanfic levels of hamfisted character insertion when I see it, and Kylo stinks of it like a Reylo stinks of cat litter and boxed wine. The way this character is written is like the misguided tween author on FF.Net or Wattpad who really, really wants their edgy self-insert OC to be some kind of tragic victim, so they write all of the prestablished characters like abusive assholes--bending them out of character--in order to elevate their character. Or they'll force their ship into reality by breaking up existing couples, and forcing together couples without any sort of in-universe justification. These type of writers do this because they're so creatively inept, that they can't find a way to organically accomodate their ideas, so they just whimsically break canon to satisfy their creative impulses. It's the glaring mark of a misguided fanfic author, and it's on full display anytime Kylo is on-screen.
And what the writers don't even realize with their exhaustive attempts to trace Kylo's growth and origins to other people exclusively--neglectful parents, abusive uncle, an evil Sith filling his head with false voices of Vader--is that they've unintentionally created a villain with no agency. This character has no real motives or actions of his own, at least not ones that can't be attributed to other characters being mean to him or remotely manipulating him, a la Palpatine. He doesn't have the obsession with attachment that drives Anakin, or even the closed-off philisophical sense of martyrdom that Jacen has. They put events into motion, and have sole-ownership of their actions and goals. But Kylo? This stupid raging incel just accelerates to different points of the story because of the whims of other characters--because Mommy and Daddy didn't pay enough attention to him, or because Darth Vader told him to in his head, or because Rey finally brushed hands with him. He's driven solely by the actions of other people, and has virtually no character agency as a result. The story splits itself in half to create forced drama around him that doesn't come about by his hand, but by the way other characters treat him. By what his current Dark Side Master tells him to do, or whether or not Rey rejects his advances.
Ultimately, Kylo Ren is little more than an object of forced, vapid drama that came at the cost of not only the entire emotional subplot of the new films, but the integrity of the pre-established characters. The writers wanted so badly for the audience to care about this sniveling cretin that they actively downgraded existing characters to placate his navel-gazing self-victimhood, to make him some kind of "pOoR aNd mIsUnDeRsToOd" ornament of Tumblr landwhales. And by doing so, he helped open the franchise up to the narrative sensibilities of woobifying harlequin romance, with all of the pants-shittingly retarded romance writing and abusive undertones inherent to that genre...spawning the loudest, most insufferable kind of Star Wars autism in the form of Reylo's, who are the uncontested rock-bottom of the fandom.
Nothing, and I repeat, nothing good came from the creation of Crylo. If I have a seething hatred for any focused part of the ST, it's for this abortion of a character...for what he did to the story, and the fandom blight he brought to the franchise.