Toxic employees exist at the extremes of those buckets. Avoid hiring toxic employees, but the filters available to you might not be good enough to screen them out, so fire them quickly. During the interview, you might just be able to observe minor quirks which are hardly indicators either way.
I cringe whenever I read job ads that are aiming for a culture fit: "we only want to hire harmonious, independent, extroverted employees;" when in my experience, the best employees do not hold strongly to those ideals, but neither to do they hangout at the other extremes.
