before the soul eater fight, he slogged through each floor practically without rest and picking up gear from dead people sent to the same dungeon. Gear is explained as something that couldn't be taken away by the goddess so there were a few that really helped him out. Also each floor that he went through, monsters would constantly show him how they are still constantly defiling the bodies of other people and pretty much taunting him that he would end up the same. In this chap, it's mentioned that he has food/water issues but that's non existent in the WN. So by the time he beats the soul eater, there's a whole chapter dedicated to the people who went before him.