Ironman/Dr. Strange vs. Thor/Loki
Ironman and Dr. Strange vs. Thor and Loki
All combatants are their strongest versions. All are equipped with their latest toys and gadgets though Strange DOESN't get the time stone. Loki gets his scepter but is not allowed mind control.
Combatants' knowledge of each team is limited to their interactions in the movies, which means they know about as much of each other as they gathered during their interactions with each through previous movies but won't know about each other's newest capabilities as of IW (since they never met during IW). IM and Dr. Strange have already fought together at this point so they'll have some experience of working together.
Fight takes place on Titan. No prep. All are going for the kill. Fight ends when all members of one team are dead.