Too many to count.
FFX and FFXII because they were boring.
I've semi-given up on Atelier Ryza because there doesn't seem to be much plot, it's like a slice of life JRPG without any real stakes or anything there to motivate me to push on (but I'm probably gonna pick it back up at some point cus I didn't totally hate it, and tbf I did reach a point in the story after 40 or so hours where the story took an interesting turn).
I've also semi-given up on The Witcher 3 because it's dragging like hell. For a game that's supposed to be one of the greatest of all time, it takes fucking forever to get to the point. Unless the point is to send you on wild goose chases whilst doing errands for people you don't fucking care about, in which case ten outta fucking ten. The RPG elements of The Witcher 3 are also kind of bizarre, and feel really weird in action, like the combat system, the healing system, and the fact that you can't find a decent set of clothing for Geralt that won't make him look like an actual clown.
Dragon Quest XII S, right before the final final boss, because the "true" story ending was so fucking awful.
Xenoblade 2 because it's boring, the mob spawns were designed by an austist, the battle system is fucking atrocious, the dub is awful, the character designs are terrible, and it's overall probably the worst JRPG and general RPG I've ever played,
Red Dead 2 because it's less interesting semi-realistic wild west setting and more horseback riding hold-X simulator,
Rise of the Tomb Raider, which is kind of tragic considering I really enjoyed the first one, but this one isn't even remotely interesting, and the fact that they're emphasizing really hard on the open world in this game (versus the pathway-type open world the first one had that complemented its story really well) really didn't do it for me.
Life is Strange: Before the Storm, I hated the first one's ending but I got this one on a really good sale. It's too fucking boring.
Borderlands 2, because for me, it took way too fucking long to get through, and the characters are absolutely insufferable.
Assassin's Creed Black Flag, while I did somewhat enjoy the pirate ship fights, I enjoyed even more the traditional AC playstyle, so I neglected the Jackdaw a lot. There was one mission toward the end that you literally could not beat unless you upgraded the Jackdaw a LOT, and money was near impossible to come by unless you were willing to take a day or two to no-life the game. Fuck that.
Kingdom Hearts, the combat system was atrocious and I keep hearing about how the story makes zero sense, so I'm not sure why I'd want to play a game when I'm not going to be able to understand the story or enjoy the flow of combat.
And finally, last one of the top of my head is Days Gone, because I couldn't enjoy the game while I was worrying about the extremely fragile motorcycle all the fucking time, and the HOARDS of zombies ALWAYS show up at the worst moment and take you VERY off track, ESPECIALLY when you're trying to service your motorcycle. Days Gone took a really neat idea of an open world TLoU zombies game and fucked it into the ground.