noun which may take the genitive case particle 'no'
Describes a person or thing that is completely unhelpful or fails to serve its purpose. Often used as a derogatory noun for a person.
彼は何もできない役立たずだ。
He is a useless person who can't do anything.
This tool is broken and useless.
役立たず literally means "of no use" and focuses on uselessness, while ヤクザ (as an adjective) also implies disreputable or shady character.
Compound of 役 (role, use) + 立たず, the negative continuative form of 立つ (to stand, to be useful). Literally 'not standing in a role', i.e., useless.