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No.1 Ask him what his responsibility is
no.2 Get your teammates together and ask around who are having
trouble with your self appointed leader
no.3 gather your teammates to meet the lecturer/tutor/teacher and
complain.
no.4 drop the bomb on him
Never ever let him know what you are all up to because some jerks
can prepare "work" quickly. Xian xia shou wei qiang ( strike first
before your "enemy knows")
This lesson comes courtesy from my previous personal
experience.