Both Meng Hao and the black-robed man unleashed the God-Slaying Fist!
It was the last of the three body cultivation fists, which combined the will of extermination, the voluntary self-immolation for the sake of bedevilment, and materialized the will of slaughtering gods. It was... the God-Slaying Fist!
Furthermore, because Meng Hao had the accumulation of the qi flow of the Windswept Realm, it also had some of the will of Heaven in it, making it the absolute peak fist attack of the Immortal Emperor Realm.
As for the black-robed man, his God-Slaying Fist came from having experienced countless bloody battles. He had honed his killing will to the extent that apparently... he had actually killed Gods, and fused that will into his fist strike. When he struck out, Heaven and Earth crumbled, and a massive wind kicked up.
The two of them shot through the tunnel like lightning, their fists on a direct collision course.