Synonyms for Unreformable (same or very similar meaning)
WordNet sense 1 (insusceptible of reform):
irreclaimable, irredeemable, unredeemableWordNet sense 2 (morally bad in principle or practice):
wicked, wickedWordNet sense 3 (unrepentant and incapable of being reformed):
unregenerateWordNet sense 4 (impervious to correction by punishment):
incorrigibleFrom the ODE community, based on WordNetadd/edit