Critical Oversight

Noun.

1. Completely disregarding or overlooking something crucial that results in a catastrophic end.

Dude Man 1: How much gas is in your car?
Dude Man 2: Not enough to get to the gas station.
Dude Man 1: How much was left when you got in your car?
Dude Man 2: Didn't check.
Dude Man 1: Critical oversight. Dumbass