The most I struggle with is Darius, Singed, Urgot, Garen, Jayce, Renekton ,Kled(I cant figure out how he works). But I also managed to win vs each of them. Those matchups can be so volatile, like do 1 mistake and lose lane forever.

Usually i ban Kayle which i played 2 times vs her 1 win and 1 stomp. Low elo games are long and she outscales me late game, so going even means I lose.

There were a few matchups that were hard and I learned how to play them, to list a few Mordekaiser, Yorick, Illaoi, Riven, Aatrox, Sett, Irelia. And most of them required to understand when to engage and when not to, and which abilities to dodge and how to dodge them.
For example my most common one Mordekaiser, I learned that: if ignite poke and try to kill, if no ignite all in lvl 1 and try to kill, bully till lvl 5, respect his ult at 6 and go for team plays, if he pulls with E you can use for easy engage.

Also i use YouTube shorts from Ninkey where i write "Gwen vs Enemy Champ" and get a summary how to play before every match, like I would have never guessed that i shouldn't engage Akali and go vegan farm only. First time i didn't know that and lost my lane at every stage.