inept
adj.having or showing no skill. You use this to describe someone who is very bad at a task or job.
adj.lacking skill or competence in a particular task or role. Often used to describe social or professional failure resulting from a lack of ability.
“He is an inept cook who always burns the toast.”
“The public lost confidence in the government after its inept handling of the economic crisis.”
“While his technical knowledge was impressive, his inept management style eventually alienated the entire department and led to a significant drop in productivity.”
Often used predicatively after linking verbs like 'be' or 'seem', or attributively before a noun.
Borrowed from Middle French inepte, from Latin ineptus, from in- + aptus (whence English apt).
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.