Thor had told Natasha and Lady Sif about each other, saying how the other was a great warrior and that he thought they would get along well. When they finally met, they allowed Thor to introduce them, and shook hands before instantly flinging themselves into a fight. Both the Warriors Three and the Avengers went to break them up, but Thor and Clint prevented them when they realised that the two women were just testing each other. The Warriors Three cheered for Lady Sif, while the Avengers cheered for Natasha.
Eventually, Natasha and Sif hit a stalemate, each holding the other so that she could not move.
They agreed to a draw and have been fierce friends ever since.
Submitted by april-december