Re: Lone Wolf..
1. By the law of averages, at least some of the team will be either already competent or teachable.
2. So it is fair to say that the "toxic lone wolf" is one who hoards information and doesn't share it within the team, and actively works to prevent the others from getting anything done.
After all, if one really is the most competent person around, what harm is there in sharing information?
And the reality in a team is that people tend to be different, and each one has their own area of competence (or in the case of junior members, potential to become really good in one area or another).
Personally I've tried to stick it out in this kind of situation, hoping that the person in question would change, but it wore me down and in the end for my own sanity I had to quit.