Do you want to compare Sif with U.S.Agent? Discover the powers, weakness & weapons of Sif and U.S.Agent from Sif Biography and U.S.Agent Biography. Find out all about Sif and U.S.Agent.# Check out how is Sif unique and distinct from U.S.Agent. Discover their love interest, sidekicks, family tree and the movies and games list in which Sif and U.S.Agent have appeared. Find out everything about them here!