Guo Gang's breakthrough wasn't accomplished alone but consecutively by two Angel Envoys, the Cyclops Giant Monster and the Cursed Tiger, both of whom had completed the Divine Initiation Ritual.
He had been accumulating for a long time, and after the ample war in the west of the city, he had more Contribution Value, hence it wasn't strange that he managed the breakthroughs sequentially after exchanging for injections.
The path chosen by the Cyclops Giant Monster wasn't particularly complex, using injections from the Nine-Snake Mother Tree, along with two Second Order insects, one High Grade and one Medium, he advanced to the Third Order Sickle-eye Giant Monster after the Divine Initiation Ritual.