Mundus is big, slow and clumsy. Virtually all his attacks can be dodged by angel gliding left and right, I kid you not. (If you're more ambitious, demon evade would be rewarding) After gliding away to safety from Mundus' attacks, run or angel lift yourself to his fists and whack both its health down to zero.
The only thing you may want to counter instead of evade is his meteor shot (which surprisingly does very little damage), which you can deflect back at him with some timing.
One last attack is where he spits lava all over the platform (much like Succubus) and you'll have to swing your way over to the next platform. Note that the camera often swings back towards Mundus even after you rotate it towards the angel lifts, which ironically makes this the hardest thing to do in this battle.
Best weapon to use is Arbiter. Does damage like it's end of the world.
Last updated: 16 Feb 2013