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