UNSC (SPARTANS) vs Imperial Sith Empire
Since BOTH characters originated in games, hopefully the moderator will allow this.
It's the Battle of Alderaan and Republic troops have been overrun. Sith forces are poised to capture the system when instead of facing special forces, they are ambushed and in heavy contact with 30 SPARTAN-IVs led by SPARTAN Sarah Palmer and SPARTAN-II Master Chief. Who wins this fight? Each side are equipped with their kitted with their standard weaponry.