STAR WARS WILL WIN. They've got 2 Death Stars, the sun destroyer, the Galaxy gun, the world devastator, the mass shadow generator, about a hundred more super weapons that I myself don't even know about, battle droids numbering the quintillions, thousands upon thousands of Jedi, sith, and other force wielders who have existed for a countless millennia before the formation of the galactic republic, the celestials who can also move entire star systems, the rakata, countless clones, mandalorian mercenaries and warriors who are on par with the Spartans even though they don't have any augmentation, clone commandos who have been on deaths doorstep when they went through training (they already know what brutality is they had to go through it on a daily basis), countless battleships that have been produced throughout the countless millennia of Star Wars history, their faster than light technology otherwise known as the hyperdrive can take a starship from one end of the Galaxy to the other in a matter of hours (which is by the way A LOT faster than halo's forerunner ships), the yuuzhan vong who nearly DESTROYED the new republic with ONLY BIOTECHNOLOGY (they should be a match for the flood), trandoshians are known to be one of the strongest species in the Galaxy and they could be a competition for halo's elites, the wookies who are stronger than the trandoshians will definitely be a match for the elites maybe even the brutes. So this is what happens: Star Wars can tactically draw most, if not all the halo forces to any star system. Then, with the sun crusher, blow up the sun and turn it into a supernova (just so you guys know, the sun crusher has NO shields just armor so strong that it can survive the explosion of a sun UNSCATHED). But, the Star Wars forces would leave before that happens so, yeah. The sun crusher also has hyperdrives installed on it so after it blows up the sun, it'll just jump to hyperspace and be on its merry way. oh by the way, the sun crusher is designed to be piloted by a few people so halo forces won't be able to board it or do something stupid like that. EVEN IF halo drew Star Wars into their Galaxy (like the entire Star Wars universe) and activate the halo array and killed EVERYONE with just the flood left, there's still lots and lots of droids (only in the clone wars alone which lasted just a short 3 years compare to the entirety of the Star Wars timeline, OVER A QUINTILLION BATTLE DROIDS WERE PRODUCED and that was in just 3 years) who are very very immune to the effects of the halo array will just kill and vaporize the flood (they have plasma weapons remember?). Even with the gravemind commanding and maneuvering the flood, the battle droids will still win because they have the numbers. Battle droids can't get effected by the flood and even though they're dumb as shit, they were meant for swarming their opponents in a battle and they were notorious for it. They swarm in, and crush what little tactical advantage the enemy has. That's how the battle droids work. They'll just do that to the flood and considering how they can't really feel pain or get infected they'll win. After they win, they'll get to work on vaporizing the remains of the bodies of the flood. Oh and by the way, the Kwa species developed their own space bridge technology (called the Infinity Gate). It was not only used as a transportation system but a super weapon as well.