ultra-left; far-left extremists
Refers to the extreme left wing of a political spectrum, often used for groups or individuals with radical leftist views. Can be used as a noun or as a no-adjective.
彼は最左翼の活動家として知られている。
He is known as an ultra-left activist.
The far-left faction of the party repeatedly made hardline statements.
極左 is a more common term for 'far-left' or 'extreme left', often used in news and political analysis. 最左翼 is less frequent and may carry a slightly more formal or written nuance.
A Sino-Japanese compound of 最, “most,” and 左翼, “left wing”; the supplied reading さいさよく contains no voicing of さ.