A brutal fistfight between two people without any intervention.
The term comes from the Super Smash Bros. series, specifically from e-sports competitions. This type of match is very common because Final Destination is a "pure" stage, with no platforms, walls, or slopes, so it depends only on skill.
A: What happened? Why is he so beaten up?
B: He just had a 1v1 Final Destination No Items Match with his coworker.