diehard
noun [ C ] disapproving uk/ˈdaɪ.hɑːd/ us/ˈdaɪ.hɑːrd/
顽固分子，死硬分子
someone who is unwilling to change or give up their ideas or ways of behaving, even when there are good reasons to do so
a diehard conservative/fan 顽固的保守派／铁杆拥趸
Compare: traditionalist noun