bad friend; friend who is a bad influence
Refers to a friend who brings trouble, loss, or harm rather than benefit. Often used in contrast with 益友 (えきゆう, 'beneficial friend').
He was led into gambling by a bad friend.
It's best to keep bad friends at a distance.
three harmful friends
Compound of 損 (そん, 'loss, disadvantage') and 友 (ゆう, 'friend'). The exact historical derivation is uncertain, but the word follows a common Sino-Japanese pattern for abstract concepts.