What happens when a person keeps climbing the Tower?
Yes, with each Level Up, wounds heal and the body is restored. However, mental fatigue is something that piles up. The strain a person has is something that gathers over time.
The Rankers knew this quite well, so they all agreed to climb together. It was very obvious what they were planning on doing.
—Letting the other person die!
In this world, there were many ways to get stronger. It was also possible to use certain loopholes in the System—especially if one wasn't an Evil Aligned yet.
Since the Rankers were in a Party, they must have been very certain of their Alignments, making them completely 'trust' one another.
But, these things could be deceptive.
Just as I managed to kill a bunch of people without a change in my Chaotic Neutral Alignment, the same applied to a lot of people—especially in a dangerous place like the Tower.