I love dramas where the ML is lonely/isolated or lacks self worth/self confidence. I love it when their self worth is slowly built up throughout the drama due to the care and affection of another person (can be a mentor, parent, or FL- doesn't matter), or when they find companionship and rid their feelings of loneliness. My preference is for Chinese or Korean dramas, but other recommendations are welcome.
Some examples:
Loneliness/Isolation-
I'm Sorry, I Love You (2004)- ML is probably the loneliest character I've ever seen in a drama. He longs for the affection of his mother and has basically no one that cares from him at the start of the drama. He is starving for love and affection.
My Strange Hero (2018) - Technically second male lead, but his loneliness and longing for affection is a pretty major part of the plot.
Stranger (2017)- ML has a personality disorder that causes his emotions to be muted even though at first we are lead to believe that he has no emotions at all. He is very lonely because he has no friends to care for him.
Thirty But Seventeen (2018) - ML deliberately isolates himself due to a trauma from his childhood.
Save Me (2017) - one of the MLs is lonely after he is betrayed by his best friend, causing him to go to jail, and then his grandmother dies. His mom is no longer alive and his dad is a jerk.
The Happy Loner (2017) - ML is a sweet man who desperately can't be alone, despite the fact that his desperation causes people to distance themselves from him.
Ugly Alert (2013)- ML is a very sweet brother who just wants to be close to his siblings, but they reject him at first due to a misunderstandings, causing him to have no one.
I'm Not a Robot (2017)- ML lonely because he has a disorder that causes him to be allergic to people (that's not a spoiler- the premise of the drama).
Moment at Eighteen (2019)- ML is lonely because he deliberately isolates himself and thinks that's the best way for him to live. His only friend is killed early on in the drama, causing even more loneliness. Second ML is also lonely even though he looks like he has the perfect life.
Low self confidence/ self worth.
Moon Lovers: Scarlet Heart Ryeo (2016)- ML suffers from lack of self confidence due to a scar on his safe, and a desperate longing for affection due to the cruelty of his mother
The Best of You in My Mind (2020)- Love love love this drama. ML is a sweet, quiet college boy who lacks self confidence and doubts himself so much that it prevents him from admitting that he likes his crush and poses major challenges to his archery career.
Just an Encore (2019)- ML too shy to express his affection to FL despite liking her from the very beginning. Doesn't otherwise fit because ML is otherwise pretty self confident, but I'm a sucker for male leads that are too shy or lack the confidence to confess to the girls they like.
Reply 1988 (2015)- ML's lack of self confidence causes him to hesitate in expressing his feelings to his long time crush until it is too late and she has found love elsewhere.
Weightlifting Fairy Kim Bok Joo (2016) - doesn't completely fit because ML is otherwise pretty self confident, but ML has a trauma which prevents him from performing well on the swim team.