Unimpeachable

1. adjective

   completely acceptable; not open to exception or reproach

   “two unexceptionable witnesses”

   Similar: unexceptionable

2. adjective

   free of guilt; not subject to blame

   “has lived a blameless life”

   Similar: blameless, inculpable, irreproachable

3. adjective

   beyond doubt or reproach

   “an unimpeachable source”