Doing research I found Etihad flights between SYD/MEL & AUH have 14 codeshares. (The most I could find for other airlines, including the routes served by US Airways/American, were from 9 to 11 codeshares.)
For example,
EY 454 AUH to SYD:
(S7) S7 Airlines 4605
(HM) Air Seychelles 5102
(NZ) Air New Zealand 4254
(B2) Belavia 354
(EI) Aer Lingus 8054
(ME) Middle East Airlines 6636
(KL) KLM 3938
(OA) Olympic Air 8054
(VA) Virgin Australia International 7454
(AF) Air France 3820
(AZ) Alitalia 3928
(JU) Jat Airways 8582
(KQ) Kenya Airways 5502
(AB) airberlin 4070
It seems that Ethiad, which is not a member of any of the global air alliances, has been looking to feed traffic to its Abu Dhabi hub through its strategic codeshare partnerships and equity stakes in several airlines. The airline has more than 40 codeshare partners, including JetBlue as the most recent. Additionally, the airline will build a U.S. Customs Preclearance facility in Abu Dhabi.
Air New Zealand and TAP Portugal also had many flights with 10+ codeshares. For NZ this is probably because of its remote location. Rather interesting finds.