I put the Abyss Walker King against other modded mobs
First oppenent:the mutant zombie from the mutant creatures mod
The abyss walker king won.
second oppenent:The Nether Raiser from the TDP addon
The nether raiser shot fireballs and punched the abyss walker king but lost shortly after
final oppenent:The Ferrous Wroughnaut from mowzie's mobs
They clashed and after a long fight...Ferrous Wroughnaut won without taking ANY damage.