Unassailable
Part of speech: adjective
Definition: secure against attack; impregnable undeniable, incontestable or incontrovertible
Untouchable
Part of speech: noun
Definition: A criminal so adept, they cannot be arrested (effective bribes securely in place.)A pariah.(Dated) In the Indian caste system, a member of the lowest caste.An incorruptible law enforcement agent
Part of speech: adjective
Definition: Not able to be touched.
Example sentence: Even tax breaks that are supposed to help the middle class too often skew toward the wealthy. Consider the mortgage interest deduction. While political leaders in both parties have long considered it untouchable, it actually helps those at the top of the income scale far more than those at the bottom.