Unjustifiable

Dropping nuclear bombs on Hiroshima and Nagasaki is unjustifiable.

Dropping nuclear bombs on innocent civilians in Hiroshima and Nagasaki is absolutely unjustifiable. We're talking about weapons of mass destruction, here!

Don't try to bullshit the world with justifications about the use of nuclear weapons in Hiroshima and Nagasaki. Their use was unjustifiable. Period!

The nuclear bombs were used as a way to force Japan into surrendering. Still, it remains unjustifiable.

It was cruel and unjustifiable.

Russia started its illegal and unjustifiable war of aggression against Ukraine, and Russia can end it.

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

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.