There was the at-school dalliance with the Winter Soldier. She also married another Russian spy called Alexei. Then she headed over to America where she dated the criminal marksman Hawkeye (who was part of the reason for her defection). And that's not even the half of it. Black Widow has long been attracted to strong, usually superpowered men but has never been able to make the relationship last. She had a reasonably long term affair with Daredevil, who she fought alongside in California. She ultimately broke up with him out of frustration at his lack of respect for her powers. There was a much briefer affair with Hercules (because...why not?) and then, when Bucky Barnes took over as Captain America, they got back together. Oh and there's the whole Black Widow/Hulk stuff happening in the movies. That's an impressive romantic history by anyone's standards and that's without considering her alternate universe hook-ups (which include Tony Stark and Count Otto Von Doom).