Unfit

[Sarah]

To make unsuitable or incompetent; to deprive of the strength,skill, or proper qualities for anything; to disable; to incapacitate;to disqualify; as, sickness unfits a man for labor; sin unfits us forthe society of holy beings.

[Sarah]

[Unqualified] or [unsuitable] for a task, [inadequate] or [inappropriate].
[Incompetent] or [dysfunctional], [subpar].

[Sarah]

when your so fucked up from drugs/alchohol that your unable to do everyday activities.

[Britney]

not suitable or good enough for a particular purpose or activity:

[Julian]

(of a thing) not of the necessary quality or standard to meet a particular purpose.