useless

Without use or possibility to be used.

“This fork has prongs that are bent. It's useless now.”

Unhelpful, not useful; pointless (of an action).

“I think it's useless to keep this discussion going. It's like talking to a wall.”

(of a person) Good-for-nothing; not dependable.

“Bill never mows the lawn, takes out the trash or anything. He's useless, but I love him anyways.”

(of a person) Unable to do well at a particular task or thing. Useless is mildly insulting.

“My brother is useless at most computer games, but he is an awesome PS2 player.”