Who were the attackers of the abbasids?

It is unclear what an "attacker" is.

If it refers to the armies trained by the Abbassids, then the Mamluks (Türkic Slave Armies) and the traditional Islamic Armies are the "attackers".

If it refers to those empires which opposed the Abbassids militarily and offensively, they incude: the Spanish Umayyads, the Idrissids, the Aghlabids, the Fatimids, the Tahirids, the Samanids, and the Mongols (who finally finished off the Abbassid Caliphate with the Siege and Massacre of Baghdad in 1256).