I think INTJ's are the best leaders. However, the only downside is that they may not actually want the position of leadership. I think they're less tolerable of bothersome people. I believe INTJ's reported that they have the least satisfactory relations with people during public workplace.However, I think extroverted judges do well.
In my own personal experiences of bosses/leaders I've had...
The best leader of a group I've had was likely an ENTJ. Regardless of type, why I think he was good was:
1) He set clear direction for the group, and that direction was actually inspiring.
2) He was knowledgeable about the work being done, and could actually help out instead of just barking to go faster.
3) He took the time to understand his people.
4) He kept group standards high.
I think these are things any type can do.
I've had an ENTP boss who was similar too.
I should mention that the second worst leader I've had was also an ENTJ, but that's a topic for another thread.
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