Looking for another way to say 'someone is incompetent of carrying out an assignment"
Solution 1:
"Unfit" is both technically correct, and generally understood.
Usage can fall into the forms of:
- Unfit noun: "Unfit mother", "Unfit leader"
- Unfit for ____ : "Unfit for motherhood", "Unfit for leadership"
- Unfit to _____ : "Unfit to Parent", "Unfit to lead"