Schrodinger's initiative

In DND... You and your team have to roll for initiative against a creature that is rated at a CR high enough to wipe out your party in one round.

New player: I'd like to take a swing at Santa.
Vertern player: no you don't.

New player. Does a 21 hit?
DM: not even close
Vertern player: Idiot! Santa is a level 20 Arch Fey!
DM: someone's on the naughty list, roll for initiative.

Vertern player: dead or alive, this is a Schrodinger's initiative. We dead, no cap.