WordNet sense 1 (incapable of being questioned):

unquestionable

WordNet sense 2 (free of guilt; not subject to blame):

blameless, inculpable, irreproachable

WordNet sense 3 (free from evil or guilt):

guiltless, innocent, clean-handed

WordNet sense 4 (completely acceptable; not open to exception or reproach):

unexceptionable

WordNet sense 5 (worthy of acceptance or satisfactory):

acceptable