Generic techniques – How can I convince my group that he has to discipline his killer?

introduction

I imagine that most of the GMs have already had a group of murderers during their sessions and that there are several good answers on how to react, these discussions have good answers, but I'm afraid that my problem is a little too complicated for a general punishment.

History

I've already been dealing with some murder-hobos, but most of them were only a few in a group that was strongly opposed to them. A few months ago, I launched a new homebrewed campaign, which started well. Most of my players are rather reserved, so most of the actions of the group as a whole are decided by a few, who take the initiative. One of these players is my star player. He has been playing Pen & Paper for years and it's a pleasure to have it in my party because most of the less experienced players take their time to do anything and are rather reserved.

Unfortunately, it also has a fairly high temperament and a very aggressive atmosphere. He gets angry quickly, takes personal things and becomes cranky and noisy as soon as things do not go his way. NPCs who are hostile or offensive end up very quickly on the list of victims. This happens fairly regularly, while the band plays as Witchers, who are not treated with much hospitality. He does not care about NPCs, conspiracies to kill guards and royalties and beats traders into submission because he claims they did not respect it with their prices. He played a murderous viking in a one-way adventure that I had before and now has a rather weak and laid-back character, but does not play it much differently.

Punishment

I've thought of several ways to stop him from abusing these people, but I doubt that any of them can help him. I thought about …

  • Reminding him to act according to the rather gentle character of his current character (that's it's done)

Problem: His personality is clearly reflected in his character and I doubt it is a long-term solution. I've already had a conversation with him, after he complained – of his character – about how the Dungeon Master inflicts too much damage and quits the fight, slamming the door in the manner of An offended teenager. It has improved, but not for long.

  • Remove it from the group

Problem: As I said, he is one of my most active players. He advances my plot and the group would suffer greatly without him. (We had sessions without him, so I know others are not just intimidated)

  • Punish them for their crimes

Problem: I intend to do it one way or another, but I'm afraid that the general punishment will have an entirely different effect, my violent player becoming even more enraged while the others would be trained to commit even more crimes. . I even had a campaign that ended in a mass suicide, because I had some killers in my last group, who thought the best idea for getting rid of it. encirclement of a superior enemy was to decapitate, gut or ignite the few important prisoners that they had previously taken.

I also thought of a way to punish only my problem gambler, but I did not find a way to not give the impression that I was taking him for cause, which would make the situation worse. It would also make no sense that the villagers do not condemn the entire group of foreigners, if their supposed leader has just reinforced their prejudices.

Question

The best way to solve this problem would be if he was disciplined by his teammates without me acting. In this way, he will not feel unjustly punished or driven to role-play against his belief. Unfortunately, I do not see how others could express themselves to stop this decline and go crazy, without letting them end on the gallows.