I've been watching Avengers: Earth's Mightiest Heroes, and I was wondering if the Black Widdow is a traitor arc was something they made up for the show or if it came from the comics?
its from the Ultimate line of comics. i could be mistaken, as i haven't read very many Ultimate comics. in the regular 616 Marvel Universe she worked for the Russians before defecting and joining the Avengers.
Widow was a double-agent for the Liberators in Ultimates 2. She totally killed Jarvis. And Ultimate Jarvis was great.