Supes is Hulk, Thor, Captain America and Iron Man combined. He would have been able to beat up all those Leviathans, beat Loki to a pulp and take care of all those minions.
All Loki would have to do is teleport to a dimension with a bunch of green, glowing rocks and bring some back. That wouldn't be a problem for Hulk, Thor, Cap and Shellhead.
How would that work out for ol' Supes and Zod?