We don't know what Mario has against the Halo universe, or why Spartans can't stand denizens of the Mushroom Kingdom. But, senseless though it may be, the two worlds have met again on the battlefield and, as you can see after the break, the conflict makes their last meeting look like a tetherball match.
Now that the ground is littered with helmet fragments and soaked with the blood of Yoshis, can the two move toward peace? Or at least unite in a mutual hatred of Kratos? Only time will tell.