characters who start off as cowards

any one know of any good dramas where character starts off as a coward and through force of circumstance grows a back bone.

please mention the name of the character.

thanks in advance.

• Big Mouth-The ML was a coward but had to adapt 
• Call It Love-ML let himself be a doormat his whole life and slowly changed but not in a dramatic way
• Insider-ML was weak and tricked. He was forced to adapt to life in prison mentally and physically
• Shark: The Beginning-ML was bullied in school and ended up in prison. He had to learn to fight and get stronger in prison
• The King of Pigs- The kids who were bullied heavily grew up to be adults who took on various paths
• The Uncanny Counter-ML was bullied and crippled. He gained powers and had to fight stronger opponents
• Imawa no Kuni no Alice+Imawa no Kuni no Alice Season 2-ML had to learn to survive beyond playing video games or die
• Sweet Home-ML was a loner orphan with low self worth but turned into a zombie and had to grow

Psychopath Diary - the ML

Yook Dong Shik is a 34-year-old office worker who is so weak and timid that he is used by everybody around him. After an incident, he becomes the scapegoat of his company, and so facing losing his job and his family turning their back on him, he decides to commit suicide. While doing so, he unexpectedly stumbles across a murder scene, but gets into an accident while running from the murderer. He wakes up with amnesia with the psychopath's diary in his possession. With no clues to his true nature other than the diary, and his fragmented memory lining up with the diary entry, he begins to believe that he is in fact a psychopath serial killer.

Introverted boss

ML - Eun Hwan Ki played by Yeon Woo Jin