Unjustifiable
Part of speech: adjective
Definition: That cannot be justified, excused or pardoned
Indefensible
Part of speech: adjective
Definition: Not defensible; not capable of being defended; vulnerable.Incapable of being justified or excused; inexcusable; unpardonable.Incapable of being explained; untenable; insupportable; invalid.
Example sentence: It is indefensible that IRS Commissioner Koskinen has not been held accountable for failing to meet his legal obligations. This is exactly what the American people are tired of when they say that our government is on the wrong track.