Nezuko's Self-doubt
Following her trial, Nezuko has proven herself an ally of the Demon Slayer Corps and Kagaya Ubuyashiki, leader of the Demon Slayer Corps, has granted her permission to continue fighting as a member of the Corps. Although Tanjiro and her friends believe in her, Nezuko can't help but wonder if she can really defeat Muzan Kibutsuji. She lives with the constant fear of losing control and hurting someone she cares about, especially Tanjiro and the others. Nezuko wonders if she's even worthy of being a demon slayer.
A not so fun fact about my interpretation of Nezuko: She sometimes views herself as a monster.