Answer: Expressive
Explanation: An expressive leader is used to describe a head or superior who is open-minded and maintains a warm and healthy cordial relationship between members of his group. Such leaders are focused on maintaining cohesion within the group rather than creating a distinct boundary between himself and his members.
In the scenario above, the position taken up by Joe highlights that of an expressive leader who seeks to maintain group cohesion and harmony by mediating in conflicts and striving to reduce recurrence of future conflicts.