1. move to heaven

2. run on (started in 2020, ended in 2021)

3. my name

+ happiness

One The Woman

Squid Game

She Was Pretty (it's old but only watched it this year and the theme song i still keep on my spotify playing agian and again haha)

1. Vincenzo

2. Hotel Del Luna 

3. Space sweepers

1. Squid Game

2. D.P.

3. Racket Boys

1. Vincenzo

2. Beyond Evil

3. My name

 Baklajan:
  1. Mr Queen
  2. Beyond Evil
  3. Youth of May

This is my list too

I've only watched 4 K Dramas released in 2021, and 3 of them were bad, scoring 5.25/10, 3/10 and 1/10 - so  my best of for 2021 is exactly 1 K Drama, that I scored at 10/10 

Check Out The Event

1. Bad Buddy (Thai BL)

2. A Tale of Thousand Stars (Thai BL)

3. More than Blue the series (Taiwanese Drama)

Hmmm probably 

Happiness

My name

D.P

not in any particular order.

 annie:

This is my list too

We think alike.

1. D.P.
2. Beautiful World
3. Good Manager 

I have 4 best of 2021 with the same rating of 9.5, but since Vincenzo is named so much already I'll leave that one out.

1.  Nevertheless, 

2. Doom at Your Service 

3. Kingdom: Ashin of the North 

 izneoleoz:

1. Bad Buddy (Thai BL)

2. A Tale of Thousand Stars (Thai BL)

3. More than Blue the series (Taiwanese Drama)

Not one of these is Korean. This thread is in the Korean Dramas forum, so it seems likely that the OP wanted replies about the respondents' picks  for best Korean Dramas. My answer would have been different if I had ignored that detail as you did

Based on the ratings of the handful of 2021 releases  I watched:

1. My Roommate is a Gumiho (9.5)

2. Taxi Driver (9.5)

3. Police University (9.0)

Flower of Evil

Beyond Evil 

Neko