Unassailably

Blank sightless eyes closed speechless mouth destined eternally to rigid frigidity (frigor mortis). Impenetrable, not an orifice in sight. Inviolably inviolate body unassailably confined within a wall of stone ("leda, lada, aflutter afraida, so does your girdle grow!").

Contrary to his assertion, however, virtually all relevant researchers say the link between CFCs and ozone depletion is based on unassailably solid scientific evidence.

[H]owever hard she pushed the tough-talkin' shtick, she remained doe-eyed, glowing and somehow unassailably demure.