unpardonable (adj.)
- abominable
- arrant
- atrocious
- bad
- base
- black
- blamable
- blameworthy
- criminal
- damnable
- dark
- disgraceful
- evil
- execrable
- flagitious
- flagrant
- foul
- heinous
- improper
- indefensible
- inexcusable
- inexpiable
- infamous
- iniquitous
- knavish
- low
- monstrous
- naughty
- nefarious
- peccant
- rank
- reprehensible
- reprobate
- scandalous
- shameful
- sinful
- unconscionable
- unforgivable
- unjustifiable
- unreasonable
- unspeakable
- untenable
- unwarrantable
- unworthy
- vicious
- vile
- villainous
- wicked
- wrong
