This is not, in itself, a reason to hate Best. Being scared when you see a literal void rushing up to meet you is pretty morality-neutral.

And even so, the Best we saw in Chapters 9 or 10 could have probably kept his composure in this situation. But that was a Best whose assurance came from the certainty of his heroic destiny. For all his furious denial now and later, he will never recapture that certainty. Some part of him knows that what he has seen in the basin is true.

That part of him may even be aware that his recent actions may have helped make it true.