There's really not a lot of advice you could give to dissidia sice it's mainly about your fighting skills...
If you absolutely can't beat him in a normal fight, try avoiding him until you can use your ultimate technic, then break his moral and finish him off.
It's mostly not too hard to flee from the comp in a fight though it's still risky since the comp will also dash to the item-thingy to get his ultimate.
