I've found that the shield toxic people have around them is often a self-fulfilling prophecy. Leadership can be in a difficult position, because their interface to the people suffering the toxic element is often through the toxic element -- and the same is true in reverse -- which masks the problem. Leadership might think "this person is unpleasant to work with" but also think "their team is delivering so they must be doing something right!" which a team can perceive as protection or an endorsement from leadership, but can be challenged quite easily by demonstrating that their behaviour is harming the team.
Even if you're confident they do have immunity, and that there's no way to pierce through their immunity, there's still opportunities to have a positive impact. A great place to start is with junior employees: every time there's an incident, reach out to them and let them know that this behaviour isn't normal or acceptable. Junior employees are in the worst position: they don't know what is normal and what is not. As a senior employee, you can say with confidence whether behaviour is normal or not, and so just saying "this is not normal" can make the world of difference to someone junior. Also, depending on the organization, reporting incidents can be useful even if it feels like you're just shouting into the void: you never know when these reports will come in useful.
As a Software Engineer, I consider it my obligation to ensure that people across an organization understand that it is not normal and not acceptable for a Software Engineer to be rude, angry, grumpy or dismissive. The genius mystique must be defeated. I behave as an activist employee: if there's a nerd bringing shame upon nerd kind, I make sure to tackle it head-on. I implore everyone to be activist employees. A nerd who berates someone? Your new mission is to get them out of the organization, and teach everyone who has been in the blast-radius of their bullshit that they were not a god, that their behavior _was not worth it_ no matter how good their code was. You'll change lives for the better, more so than your code ever will.
Even if you're confident they do have immunity, and that there's no way to pierce through their immunity, there's still opportunities to have a positive impact. A great place to start is with junior employees: every time there's an incident, reach out to them and let them know that this behaviour isn't normal or acceptable. Junior employees are in the worst position: they don't know what is normal and what is not. As a senior employee, you can say with confidence whether behaviour is normal or not, and so just saying "this is not normal" can make the world of difference to someone junior. Also, depending on the organization, reporting incidents can be useful even if it feels like you're just shouting into the void: you never know when these reports will come in useful.