Yo I?m looking for an heroine or an hero who is rejected by everyone because of her/his power or because she/he is a monster.
Someone like Zero two from Darling in the Franxx.

Thank you for your reply.
😀

Sorry for my bad English 😉

There are many manga that starts like this but mc is not lonly at all after a few chapters. Like Naruto.

Berserk and Noblesse manga got mc with kinda lonly vibe. Even they are not total loner but at least they don't start dancing at the first sound of so called friends.

Arguably, Natsume Yuujinchou fits. Ever since he was little, he was rejected by society and written off as a trouble-making weird kid, because the spirits only he can see are scary, often malevolent and people believe he's hallucinating. Throughout the story he earns more acceptance, but still stays a loner. Episodic, but with beautiful (albeit, slow but well paced) character development. And ignore the Shoujo tag, seriously, this is a gem that could be appreciated by any demographic. It's intelligent and heartwarming.