He has finally defeated his long-time rival to win the championship title.

rival 是名词，意思是"竞争对手"或"敌手"，指在比赛、竞争或对抗中与自己争夺同一目标的人或团体。这个词来自拉丁语 rivalis，原指"住在同一条河两岸的人"，因为水资源常引发竞争，后来引申为"竞争者"的意思。