Most of these that I am mentioning is the male lead/leads being seen as unworthy or themselves feeling undeserving.
cruel city aka heartless city : the male lead has to deal with a lot and feels like his life is dangerous while the female lead wants to get involved and get to know him along the way
Just between lovers: both have experienced traumatic events in the past, while the ML is struggling to get by
come and hug me: Also both experienced a horrible past but are there for eachother while ML doesn't think he should be affiliated with her because of their past circumstances
the smile has left your eyes : the ML seems very suspicious under many circumstances and the FL is the only person to believe in him
glamorous temptation: not really beast ML but he has other priorities, and the drama gives the same aura that Mask gave me
love me if you dare: This is a chinese drama but one of my faves, the ML in the beginning is seen as very secretive and scary.
when a snail falls in love: another fave chinese drama, the dynamic between leads is similar to love me if you dare
misty: this one also isn't much about the MLs but it gave me the same feels as Mask
moonlovers/aka scarlet heart: the ML has a scar that he believes makes him look like a monster while others have called him that too.
the last empress: one of the MLs is seen as a monster throughout the drama but tries to redeem himself
ms.perfect: this one also isn't about the ML but it also gave me similar feels to Mask
I did not talk much about the FLs because I feel like they are all smart and good :D enjoy
I tried to do my best on the descriptions without giving out to much, let me know if you'd like to know more.