Kain versus 343 Guilty Spark
I searched my mind high and low for a soulless, bloodless, and mindless enemy that was still sentient enough to fight. Then, the insane A.I., 343 Guilty Spark, came to mind. He's fast, annoying, and has that very powerful laser. Since he has no soul, Kain's sword can not steal it, and since he does not have blood, blood burst won't work, and finally, since he has no mind, madness cannot be induced upon him.
This battle is being fought on The Ark, and Kain is at his full power, and 343GS has all of his given abilities as an installation monitor.