First post here, so I apologize for breaking some conventions that I don't know about.
I am currently guiding a group of six through Tomb of Annihilation (I will not take care to avoid spoilers, so you will be warned beyond this point). The campaign is decent. The group of players is a little rockier than I'm used to, but overall I'm pretty confident that all of my players can have fun.
My problem is with one person. My group of players is mostly a mix of nationalities, so we're playing on Roll20, but two of them are real friends of mine. One of these friends always told me that he likes the "game" part of D & D 5e more than role-playing, which is fair for me. Not everyone likes the same things about D&D and he happens to prefer mechanics and stuff. He knows that I include a healthy part of role-playing in my campaigns, but I also like to provide challenging and interesting content that does not involve role-playing.
My first alarm bell should have been ringing when he intentionally made a dumb character (An Aarakocra Monk) so that he didn't have to do that much RP. I didn't think about it much at the time because his character communicated in writing and he had agreed with another player to share a back story. While this player was actually taking a back seat to RP, he was still involved in the game. This has changed over the course of the game. As time went on and when everyone was chatting and having fun, he became more and more withdrawn, just not role-playing and just there to play. I have spoken to him several times during this time, but he assured me that he was enjoying himself, so I let him. This situation became devastating when the character he shared a background story with died and he did absolutely nothing in the character to respond to.
Over time, he also stopped talking less in our conversations outside of the characters and didn't just play role-playing games. He limited his in-game interactions to throwing only when I asked to declare his attacks and ask if he could craft items during the trip. At that time, he also unlocked "Stunning Strike" as a monk and used it constantly to gain an edge in combat. That's okay, of course, but his interactions were limited to just rolling his attacks and explaining that he used Stunning Strike.
Finally, the situation came to a head when the group took on Tzindelor, a young red dragon. The party was well prepared and had already caused massive damage. This player came and did the Stunning Strike as often as he could. Tzindelor passed most litters, but critically failed a check, which means she would be stunned and this epic fight everyone was thinking of (it had only taken a round or two at that time, her health melted ridiculously fast) ), would have been reduced to The group just hit a sandbag on HP. At that point, I made a quick DM-Fiat decision and said that Tzindelor had legendary resistance.
Now we can all discuss whether this was appropriate or not (please add a side note in your answer if you'd like, I'm interested in other opinions), but the point is that this player is also frustrated by this. Immediately after the event, he found the magic big ax in the dragon's hoard and refused to give it to the barbarian in the group, although he cannot effectively use it as his current character.
Other players asked in the character whether he wanted to give the barbarian (the other friend) the ax because he could actually use it. He didn't answer and just said he wanted to keep it out of the character.
I later talked to him about this special ax and just asked why he wanted to keep it. He said something about how he finally got loot. It is true that he did not have much magic items or upgrades, but on the other hand, there have only been two remarkable magic items in the group so far, an alchemy pitcher and the Ring of Winter. The ring in particular is incredibly powerful, but I'm slowly punishing the player for using it over time. (Further details on how the ring landed with the players are available on request). Finally, he gave the barbarian the ax because in real life the player of that character asked him.
Finally, I heard from another GM from another campaign that this player still brought up the incident with legendary opposition to him. I quote him completely useless. Although I can definitely understand the frustration in this particular case, I've never stopped him from using Stunning Strike, and I really believed that the fight was more fun. I would like to offer compensation, but I have no idea what to do as he doesn't play an RPG and spams only Stunning Strike. I will definitely make him whine about a boss someday, but somehow I don't think that really fixes that much (confirmation bias is a pain).
I have invited this player for a personal interview in the coming days. Can anyone give advice on how to talk to this player? Suggestions on how to better enjoy the game would also be appreciated. I will provide the desired details and will provide an update after the interview. Right now I'm thinking about just asking him what he wants and what I could do to help. If we can't find a solution, I carefully suggest that this game may not fit his style of play and offer him the option to exit the game. I'm not going to tell him to go. If he leaves, it will be because he agrees that it is the best.
I really hope to find a solution. The tension that caused this not only killed his enjoyment of the game, but also affects the atmosphere of the whole group, and nobody wants that.