He can only use Cross Slash is he hits Ness. Ness just has to concentrate to attack Cloud with his PK abilities. Long range or short range.

And Ness can't fly, he has a PK-aided double jump that he uses in Smash Bros. and Smash Bros. Melee. The full double-jump gets him about 15 to 20 feet of air, and the additional triple jump (double jump + PK Torpedo) gets him another 10 to 15 feet. He's significantly more maneuverable than Cloud.