A person that is playing too seriously or trying too hard to win but on a mega level.
Some examples are below:
Using OP or Meta weapons in FPS
Camping in FPS
Raging in casual or practice mode playlists
Farming kills by knowing spawn points
A similar, interchangeable term is a ‘mega try-hard'
"The UMP 45 can carry most Mega Sweats on any Tarkov map"