Hey I'm running a 5e campaign and a certain player who is

You're stupid.

The d20 system does not allow a player to call literally any action and then roll with a possibility of success. Part of your job as DM is to tell players whether they can or can't roll for shit. You don't have to let a player roll to pluck the moon out of the sky because HURRR NAT 20 IS AN AUTO SUCCESS. It's your game. Don't let players do stupid shit.

>>54209522

Punch him as hard as you can in the chest. After he stops crying and asks you why just tell him you were trying to pickpocket his heart.

>>54209965
This.

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>>54209965

>>54209522
It'd be attack rolls to cut someone's heart and I'd really like to know how they plan to do that stealthily.

You should tell him to stop acting like he's playing Skyrim. If he doesn't understand and doesn't stop, you should punch him in the face and throw him out.

>>54209522
What else makes him That Guy?

With any other player, I guess I'd explain that we're not playing a kung fu movie, and his action has zero chance of success. If he insists, hijinks would ensue as NPCs react to him.

If he insists on holding up the other character's actions or splitting up the group to keep playing his "joke", I'd explain away from the table that what he was doing was getting in the way of everyone else's enjoyment of the game (including my own).

And/or offer the alternative that he can attempt to snatch hearts as a colorful way of narrating his sneak attack ability. 1d4 base damage for unarmed sneak attack. If he kills them in one shot, he comes away with a sticky, beating heart. People start treating him like an evil wizard run amok.

>>54209522

Don't play with cunts.

>>54209899
>not letting your characters do ridiculous shit with a DC of 20
https://youtu.be/V2XGp5ix8HE?t=1m21s

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>>54209522
Punish ridiculous decisions. Give him a sliver of a chance. Make him roll 1d20+1d10 and set the DC at 30 or something. Anything less than a perfect roll results in him punching someone in the chest, immediately alerts the local guard, and puts the party in a terrible situations.

As a DM, when you have a shitty player that you need to deal with, the first thing you want to do is turn the other players against him. Punish him for his mistakes and punish them for his mistakes. They'll get sick of his shit eventually and will back you if you ever need to tell him to fuck off.

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>>54213920
>Still give him a chance and have him roll regardless.
>Punish the entire group in a flimsy ploy to have them turn on one guy.
>Passive-aggressively rely on in-game punishments alone.
You're not a very good DM, are you? Just put your foot down out of character yourself, don't force the other players to do it for you, you coward.

If a person is acting idiotic and you won't stand for it, don't throw him a bone by giving him a chance to succeed: just deny it, talk to the guy in private or kick him out if it persists. And don't force the other, presumably innocent players to be miserable too because of one chucklefuck.

>>54213980
Depends on if you're playing with strangers or playing with friends. If you're playing with friends, it's already a miserable situation and there will be butthurt if you have to tell the guy he can't play anymore regardless of what you do.

In that situation, it's definitely important to have the rest of your friends on your side. In my experience, people who pull this kind of shit never stick around anyway. They typically flake after a couple of weeks and the game moves forward.

rule of cool and 20 auto-success can be stupidly abused.

i suggest you to make a rolled 20 counts as 25 and to interpret the rule of cool only as a slight bend of the rules to be applied by the DM when a player is doing or thinking something actually good.

traditional D&D 3.5 allowed everything to be done with skill checks. For example you could walk on clouds with a 120 balance checks.Likewise stupid bullshit like that should sit at DC 90+.

When a player ask to do a stupid shit ask him if he's sure, then proceed to make him fail and make his character suffer the consequences.The first time guards should lock him up and he should find a way to escape, the second time he get jailed properly or executed and he'll have to make another PC.
Hopefully he'll get tired of his bullshit before the rest of the players ask you to never invite him again to play with you. You should comunicate with your players and ask them what they think of your DMing and everyone's behaviour.

>>54209522
You should kick him out of the group, then stop DMing until you learn how to say no to a player.

>>54209965
THIS

>>54209522
Tell him that this is not Skyrim and he should get over it.

If he wants to kill people by touching them then have him play an Open Hand monk.

>>54209522
Even the variant rules only incur injuries on critical hits and 0 hit points. If he wants to pickpocket a heart, it at the very least should be one of those if not something more impressive.