Dastardly

das·tard·ly | ˈdastərdlē

adjective archaic, often humorous

wicked and cruel: pirates and their dastardly deeds

I rise to announce that I will bring Articles of Impeachment against the president for dastardly deeds proposed and dastardly deeds done. —Rep. Al Green

origin

mid 16th century (in the sense ‘dull or stupid’): from dastard in the obsolete sense ‘base coward’.