The Best Black Widow Villains

Black Widow has had quite the history, and to this day we still don't know most of it. She's an ex-Russian spy who (depending on which continuity you're in) has played for both sides of the Avengers. She's got villains that are heroes, and villains that are villains. She even has some enemies that are fellow codename: Black Widows. 

So who ranks as the greatest Black Widow villain? One of the Femme Fatale's like Wrangler or Elektra? One of the Marvel big bad's like Red Skull or The Mandarin? It's up to you - vote up your favorite Black Widow villain below!