I've been GMing for a while, all my players are pretty good friends. Some of them have really fit well within playing roles. They have a really great grasp of "character knowledge/information".

But one player hasn't quite demonstrated a good concept of character knowledge/information. He tries to assert himself in every situation, even when his character would have no knowledge.

For an example, his character has taken mechanics as a hobby. Another player has an old droid chassis that he spends his down time, tinkering around with - It'a an invested interest he has with this chassis. When the other player went to go poke around with his droid chassis, the asserter tried to do the mechanical tweaking on the droid himself, instead of letting the other character do it himself. The other player didn't want his help, and indeed actively ignored the requests of the other player.

Later on in that session, this player essentially was doing actions that simply put other characters directly at risk. One of characters was unconscious on a pirate's ship (The player of this character was actually not present for the session), and after hearing legitimate threats of the pirates blowing up the ship via remote detonation, he went to go steal the ship - with the unconscious character still on board. As a GM, I started to rack my brain (on the fly) within the story to where the other character doesn't get injured. I decided to just end the session on this cliff-hanger, hoping that the other character will wake up, and talk some sense into him.

Honestly, I don't care if one of my PCs do something that would kill themselves. If they want to be reckless, it's their character, and their prerogative. But he seems to be having the most enjoyment playing at the expense of the other players. by trying to compete with, or endanger, the other characters. I'm not okay with a player ruining the fun of another player within the game. If it makes sense with the context of the story's situation, and one character is trying to harm another... that's one thing. But this is just one player gaining satisfaction by causing grief to the other players.

When I talked to him, he said he was roleplaying his character's short-sightedness. Additionally, he said he simply doesn't care if his character dies - as he'll just remake basically a "respawn" of his current character. He seemed to have no care for the safety of the other characters.

He's a friend of us all. But everyone has talked to me about their own frustrations with playing with him. I know I need to talk to him, but I'm trying to keep everything as drama-free. It's just a game afterall.

I've played with him as a PC before, and he can be very difficult to play with. As a GM, it hasn't been as noticeable, but apparently it is getting worse and worse.