noun
Refers to a person who is violent, rough, or behaves in a disorderly manner. Can be used for street thugs, bullies, or anyone acting aggressively.
あの乱暴者たちは夜の公園をうろついている。
Those thugs are prowling around the park at night.
彼は
He was accosted by a ruffian and had his wallet taken.
暴漢 is a more formal or literary term for a ruffian or assailant, often used in news reports. 乱暴者 is more colloquial and general.
Compound of 乱暴 (ranbō, 'violence, roughness') + 者 (mono, 'person'). The exact historical derivation is straightforward; the word has been used since at least the Edo period to describe violent individuals.