noun
Refers to the leader of a criminal group or a rebellion. Literary and somewhat old-fashioned; in modern contexts, 首謀者 or リーダー are more common.
警察はついにその組織の巨魁を逮捕した。
The police finally arrested the ringleader of the organization.
Composed of 巨 (huge, great) and 魁 (leader, pioneer). The exact historical derivation is uncertain, but the combination suggests a 'great leader' or 'chief'.