Antonyms of adj forgivable

1 sense of forgivable

Sense 1
excusable, forgivable, venial -- (easily excused or forgiven; "a venial error")

INDIRECT (VIA pardonable) -> unpardonable -- (not admitting of pardon; "unpardonable behavior")

Similarity of adj forgivable

1 sense of forgivable

Sense 1
excusable, forgivable, venial -- (easily excused or forgiven; "a venial error")
       => pardonable (vs. unpardonable) -- (admitting of being pardoned)