Who would win? The battle would take place above Mars in a UNSC ship, then move to covenant cruiser, before the cruiser crashes into mars, and they are accidentally teleported to Hell. All weapons, all powerups, all abilities. In-game lore and gameplay only. Doom Slayer is much faster has over all better weapons. He never has to reload and can rip and tear through [u]MECHS[/u]. He is strong enough to hold a triple minigun while moving at full speed without tiring and can still jump. He is able to fall from large heights and has defeated a Titan alone. He also wields the Crucible. Master Chief is smarter and has a slight advantage in armor and regenerating shields. He has fallen from orbit and survived and manages to fight large groups of covenant troops alone. Edit: New info has arrived to me. The BFG only works on those who have argent energy inside them. That does not mean Doom Guy will get stomped. Remember the Crucible and how Samuel Hayden activates it's sword mode? That thing is a doomsday weapon. It's the signature DoomSlayer weapon and he gets it.