A ruffian, hooligan, or rogue who lacks a sense of shame or moral principles.

a local hoodlum or bully who harasses or exploits people in a specific neighborhood

Rowdy Cai (1969-), a pioneering Taiwanese Internet writer.

a soldier who behaves like a hooligan or scoundrel, typically a long-serving one who has developed bad habits and ignores discipline

yuppie (loanword, common in Taiwan)