My experience with the Italians? Well, as the Byz it was a piece of cake.
Its seem that Vestirare, Kontaroi and Paramonai were at least equal to the Pavisiers, so the Byz variety kicked in and assured victory.
The only problem with Byz troops is their upkeep, but thats not so harsh if you manage to get the Georiga Byz Egypt triangle.

As the Germans you are heavily outclassed.
Neither Saxon men at arms nor Swabian Swordsman seem to do the job, your own spears are inferior in all aspects and dont get me started about Heerbanns, they simply bounce off.
I have to employ a lot of mounted X-Bows to lure some of their units away, if there are 2 vs1 instances for my Swabians/Saxons they can actually win.
The only problem is that popolo Cav is slightly better than mtd. X-bows to.....

Hungarians can get a good laugh as the slow pavisiers try to cath their horse archers.
If the AI could actually use horse archers the Hungs might actually be able to stall the Italians.

French are not to shiney but better of than Germany.
in contrast nto the Germans they at least get bigger Knight units.
Which can counter the Pavisiers if used correctly.

Sicily can fight fire with fire or simply grab some of their own horse archers.

The thing is: Apart form Sicily who have Pavisers on their own and Byzanz who have comparable troops who cost significantly more everyone has to (more or less) rely on Cavalry multicharges and horse archers to defeat the Italians.
The Ai cannot pull of Cav multicharges at all and is pretty bad with hore archers, so the Italians nearly always win this in AIvsAI matchups.