This is kind of a two part question, firstly about the bad character thing and secondly wrangling table drama. For context, I am currently DMing D&D 5e Curse of Strahd, with 5 players. Some of you might think this is one too many which I would agree with, but our group was founded as a social thing for friends so we don't want to exclude anyone. The friend thing is also why I've been trying to avoid being heavy handed with authority.
Problem 1: player treats his characters as disposable
I have a player in my group, who I'll call Carl. Carl has a constant problem wherein he builds one-trick pony characters, gets bored with them when they aren't as good as he thought, and then stops trying to keep them alive so he can build another one. I don't approve of this behavior because a) constant character death in a story and knowledge heavy campaign like Strahd is detrimental and b) he drags the party into his terrible decisions and risks other players' characters as well. I understand that character death is a part of campaigns, but I also believe campaigns (particularly a published one like Strahd) are designed around the general assumption that characters will try to survive, so the way he plays really throws a wrench in things, especially since he's the only one doing it. To disincentivize player death I instituted a rule where the second character has to be built off of point buy stats (they all rolled above average stats at the beginning) and the third character has to use the standard array. This rule came into effect the first time Carl's character died (trying to fight Vladimir Horngaard alone) and he built his next character off of point buy.
Problem 2: The player got frustrated, threatened to quit
This last session (Amber Temple), Carl's character gained a lot of flaws from curses and his alignment changed to evil. At the very end of the session, he announced that he was attacking the party right before a long rest. He also played the "My Guy" card. As his death is almost certain next time, I told him to make a new character with the standard array. I wake up the next morning to a text saying that he's rolling stats for his new characters, and if I don't let him he's taking the Strahd book and grid map (which he had previously donated for us to use) and quitting. I managed to talk to him about it and he said he felt that I was unfairly punishing him, that he didn't think it was a problem for everyone else, that he felt his character wasn't performing as well as the other melee fighters (he's an Eldritch Knight with a Barbarian and a Paladin), and that he felt that new characters get treated badly by the existing characters and he isn't having fun. The last thing he said was that he might just quit, but leave the materials so we can keep playing.
What to do, friends?
The basic questions are:
How do I deal with a player who doesn't care if his character dies and drags the party into risky situations because of it?
How do I make this guy feel like playing again?
Honestly if this wasn't a group of friends I would have kicked him for his behavior and bought new materials, but I don't want to do that to him. If anyone has dealt with a situation similar to either of these problems I would love to hear about it.
To answer a couple comments, we are all 25. Players have expressed frustration with his play at the table, as well as to me individually. I'm hoping to resolve this between us because I think bringing it up in the group setting might make him feel ganged up on. I'm also trying to keep it between us because I think he'll be ashamed of his behavior eventually and I want to let him save face.
The Unexpected Conclusion
Well, Carl's girlfriend just went into early labor so he has to quit anyway, so this kind of took care of itself. I appreciate the input and will use it going forward.