partisan
/ˈpɑɚtəzən/ /Brit ˌpɑːtəˈzæn/
noun
plural -sans
[count] a person who strongly supports a particular leader, group, or cause
a member of a military group that fights against soldiers who have taken control of its country
adjective
[more ~; most ~] often disapproving :strongly supporting one leader, group, or cause over another
US