unjustifiable

From un- +‎ justifiable.

unjustifiable (comparative more unjustifiable, superlative most unjustifiable)

That cannot be justified, excused or pardoned.
Near-synonyms: indefensible, inexcusable, unforgivable, unjustified, unpardonable, unprovoked, unreasonable, regrettable, unacceptable, unworthy, remiss, blameworthy, culpable, unwarrantable, excessive, immoderate, unconscionable, outrageous, groundless, unfounded, foundationless, baseless, unsupported, unsubstantiated, unconfirmed, uncorroborated, invalid, untenable, weak, shaky, flawed, defective
- 1962 October, G. Freeman Allen, “The New Look in Scotland's Northern Division—II”, in Modern Railways, page 270:
  From track level, its operating floor looks particularly capacious, but there is a vacant space at one end which was designed to accommodate the control panel for the Perth-Inverness C.T.C. scheme; this was adumbrated as long ago as the 1955 Modernisation Plan, but now seems to be regarded as an unjustifiable luxury.

that cannot be justified

English