Englishdastardly
adjective
archaic or humorous
a dastardly plan was hatched to kidnap him:
wicked, evil, iniquitous, heinous, villainous, diabolical, diabolic, fiendish, vicious, murderous, barbarous, cruel, dark, rotten, nefarious, vile, foul, monstrous, shocking, outrageous, atrocious, abominable, reprehensible, despicable, execrable, corrupt, degenerate, reprobate, sordid, depraved, dissolute, bad, base, mean, low, dishonourable, dishonest, unscrupulous, unprincipled, underhand, roguish;
informal crooked, low-down, stinking, dirty, shady, rascally, scoundrelly;
British, informal beastly, not cricket;
Law malfeasant;
rare egregious, flagitious.
▷antonyms noble, praiseworthy.
dastardly Oxford Dictionary of English