noun
good-for-nothing; loser; waste of space
Strongly derogatory term for a person considered worthless or a failure in life. Often used as an insult or in self-deprecation.
あいつは生まれ損ないだ。
That guy is a good-for-nothing.
自分を生まれ損ないだと思ってはいけない。
You mustn't think of yourself as a loser.
役立たず means 'useless person' and focuses on lack of utility, while 生まれ損ない is a harsher, more existential insult implying worthlessness from birth.
ろくでなし is a common insult for a ne'er-do-well or bum, similar in strength but less specifically about being born worthless.
Compound of 生まれ (umare, 'birth') and 損ない (sokonai, 'failure, damage'), literally 'birth failure'. The exact historical origin is uncertain, but it follows a productive pattern of noun+損ない to indicate a flawed or failed version of something.