Well, it's a bit hard to say for sure. But some fans believe Benimaru Shinmon could be the strongest, given his immense power and combat skills. Different characters shine in different situations.
In the Mortal Immortal World Chapter, the strongest power in the Immortal World was the Nine Elements Temple.
Jiuyuan Temple was Samsara Temple's mortal enemy. It formed the Heavenly Law Alliance with Truth Sect, Candle Dragon Sect, Exquisite Sound Sect, Qingyuan Palace and other forces to resist Samsara Temple. The sect master of the Nine Elements Temple was one of the top mighty figures in the Immortal World. His strength was unfathomable. The cultivation techniques and magic treasures of Jiuyuan Temple were also very powerful. They were treasures that immortal cultivators in the immortal world dreamed of.
While waiting for the TV series, he could also click on the link below to read the classic original work of " The Legend of Mortal Cultivation "!