And quick knockout. Full house as well.
The rarest achievement in chess.com!?

Actually there are several dozens of scientific bases with several hundreds of people
The flag of Antarctica must be added to chess.com!

but mostly their free time is outside and if they will use a phone it will just freeze with the cold around it

but I watched a video and it says that the Antarctica award is already in but to get it you have to join some club
Chess marathon is my rarest achievement.