not capable.

not having the necessary ability, qualification, or strength to perform some specified act or function

As an administrator, he is simply incapable.

without ordinary capability; incompetent.

a thoroughly incompetent person, esp. one of defective mentality. ?

incapable of

not having the ability, qualification, or strength for (a specified act or function).

not open to; not susceptible to or admitting

These materials are incapable of exact measurement.

legally unqualified for.

adjective

capable , competent , qualified , strong

adjective

butterfingers * , disqualified , feeble , impotent , inadequate , incompetent , ineffective , ineligible , inept , inexperienced , inexpert , inproficient , insufficient , losing , naive , not equal to , not up to , poor , powerless , unable , uncool , unequipped , unfit , unqualified , unskilled , unskillful , unsuited , weak , unequal , inapt , unworkmanlike , helpless , disabled , feckless , incapacitated , insusceptible , notable , sterile , untrained