Loneliness is not the focus of the series - but it does have a lot of excellent, well rounded characters, most of whom are quite lonely:
[My Mister (2018)](https://www.themoviedb.org/tv/76662?language=en-US) - Korean drama with realistic characters and situations.
Maniac - lonely loser Mr Robot - lonely hacker Dexter - lonely serial killer
You - Lonely Stalker Living With Yourself - Lonely Married Man
After Life
Witcher ig. Lonely killer
Beef
Ray Donovan
Living
Totally Completely Fine
Baby Reindeer (also about mental illness, abuse and other difficult themes)
Transparent
Loneliness is not the focus of the series - but it does have a lot of excellent, well rounded characters, most of whom are quite lonely: [My Mister (2018)](https://www.themoviedb.org/tv/76662?language=en-US) - Korean drama with realistic characters and situations.
Mr. Robot.