If you speak French, I highly suggest you listen to Mathias Brunet's interview with Kentb Hughes, in which he makes some big statements regarding Slaf.
First one is an explanation of why they kept him in the NHL. They felt like it was the only place where he would not be able to rely on his physical advantage to win, and would have to develop other parts of his game. Or at least that he should level up in that area to keep relying on it.
Management sort of let him do his thing the first year, but at some point Hughes himself talked to him and told him he had to stop trying to play like Jack Hughes (a skill-based game) and start playing like Slaf (a power game). Essentially, Slaf is trying to be truffled fois gras when he should be accepting his fate as steak and egg.
Its obvious he has That Guy energy. He's charismatic, vocal and fearless. But is he mean? Does he want to play "f-you" hockey? That's what I wonder. It's one thing to be built like a bully and another to act like one. The latter is not a given, but I can understand that it might take time for a kid to get to that mental space in one of the toughest pro sports leagues in the world. Maybe he just has to accept his role.
Even if he never develops superstar skill, he can still be a great piece by dominating physically with the skill he's already shown. Tons of guys have become impactful wingers through sheer power.