That one which ZWJ opened with his newly mastered Qian Kun skill.
Without Qian Kun, could any of the Greats and above fighters have blasted through it?
Since ZWJ's energy might not be short of the Greats, would the Greats have been stuck in there if they were in a similar situation?
Would GJ and XF be able to concentrate their power in the Dragon Palms to blast thru without bringing the roof down?
Would DY be able to cut thru with 6MSJ?
JMZ could cut metal with his bare hands, could he cut through the rock?
Xu Zhu probably could use brute force to open the door with 1 hand.
Sweeper monk would probably find the hidden lever somewhere.....
Dugu? Opening the door without opening the door....