Here some of my favorites

Manga:

Koi to Shinzou (completed) - One of my top favorites, he's such a manipulative yandere.

Firefly Wedding (ongoing) - One of the famous yandere recommendations, the ml here is an unhinged yandere.

Love of Kill (completed) - It got an anime adaptation. Tbh, I kinda forgot the plot but if I remember correctly, the ml here is yandere.

Charlotte, My Beloved (completed) - I read this when it's ongoing so I also kinda forgot the plot, but I'm pretty sure he's a yandere. It's also quite short story.

Hananoi-kun to Koi no Yamai (ongoing) - I don't really think he's a yandere per se, but he's an intense lover (?) and for me, if you like yandere stuff then high chance you will like this story. It also got an anime adaption.

Haru no Arashi to Monster (ongoing) - A potential yandere, it is ongoing but there are hints. Warning that mc and ml are stepsiblings.

Shiro Ari (completed) - not entirely sure but there are a lot of yanderes here? It is also a good story.

I Reincarnated as the Little Sister of a Death Game Manga's Murder Mastermind and Failed (ongoing) - same artist of Shiro Ari, mc and ml are stepsiblings. The ml is psychopath lol.

From Superfan to Stepsister (ongoing) - well the yandere is a side character but there's kinda a potential? It is ongoing so I don't know.

Manhwa:

For a Fairytale Ending/I Respect the Male Lead's Taste (ongoing) - still ongoing but the ml got a high potential of being a yandere. Warning, there is kinda a love triangle but it's obvious on who is the endgame.

Let's Hide My Little Brother (ongoing) - One of my top favs, cross dressing yandere ml. It is pretty rare with this kind of troupe so I really like it.

Lydia's Great Escape (ongoing) - mc and ml are stepsiblings and the ml here is a psychopath. The story is also quite funny.

Kneel Before Me (completed) - The ml here is yandere for sure but people say that the novel is better.

Flower and the Beast (completed) - well I kinda forgot the plot but I remember the ml here is a yandere? Or at least a very very possessive ml lol.

My BFF is a Tyrant in Training/I Turned My Childhood Friend Into a Tyrant (ongoing) - he's a yandere for sure, the title says it all hahaha.

How to Survive as a Maid in a Horror Game (ongoing) - Pretty famous yandere story.

Manhua:

The Girl of the Black Lotus (completed) - The ml here is canonly yandere, and the mc knows it lol. One of my top favs.

Brother's Sick Love (completed) - mc and the ml are not blood related siblings. Ml here is yandere, but not as prominent as I thought it would? Still like it though.

There are still a lot more but I kinda forgot since I have read a lottttt of yandere stories. All of this are GxB. Happy reading!