Use your first round to cast Slow on the Monk.

It depends on the type of game you're running and its an expectation that should be set from the beginning (as is "whether a 20 is a critical skill check at all")

My games tend to be more grounded, so when I have run critical skill checks, they are a success with a reasonable bonus. A critical persuasion check might have the guard believe your phony story but also accidentally let slip some useful info as you're passing through the gates because he's let his guard down.

But in a game where the vibe is more out there and power fantasy-y, heck yeah, let your 20s rewrite reality!

At the "get out of Dodge" part of an Avernus campaign, the party had to split up to solve a puzzle to get to the top of a chained floating island. Everyone had their own last stand encounter (they knew it was coming and got to prepare). The Monk in the party just noped out and ran up a kilometer long chain watching all the mobs chasing him slowly fall away and die behind him as they chased him. Even without a nat 20 his dex was higher than a blazed giraffe.

The second lamest person in that party rode a nightmare to the top, after driving his hell machine off a cliff to get more air, he dipped, summoned his nightmare, and watched the miniboss plummet into hell lava with his death tractor. I made him roll for that shit after he announced what he wanted to do and he hit a nat 20. I didn't argue rules with the dice, it was too cool. He had crippled the things wings so it couldn't fly off. Absolute dick move on his part. All of it hilarious.

For a lot of things, my group will keep it level... But Persuasion is a free for all. And it goes both ways.

PC 1: "My Femme Fatal attempts to seduce the Orc guard."

nat 1

DM: "You attempt to talk up the muscular green bastard, who doesn't seem all that impressed. You pester him a few minutes before he snarls, pulls up his sleeve to show you the rainbow flag tattoo on his arm and says 'Fuck off, lady. I'm gay!'"

PC 2: "...Can my Engineer try to seduce the guard?"

As per Sir Terry Pratchett, a Million-to-one chance succeeds nine times out of ten.

How do you roll a zero

Edit: if thats O'Brien im guessing a transporter problem

You rolled a 1.

I'll grant you time and space.

*leaves*