According to Rosh in The Bronze Bow, what is Daniel's fatal flaw?

According to
Rosh, Daniel's fatal flaw is that he is not ruthless enough. Rosh tells Daniel,

"I've warned you before...there's a soft streak in you. Till
you get rid of it you're no good to the cause."

Rosh
had used Joel as a spy for the cause. Then Joel had been captured, and Daniel and the others are
anxious to get a group together to secure his release. Rosh, however, has no intention of
sending any of his men on a rescue mission. He says,

"On this mountain every man is responsible for himself. That holds for Joel...he
was stupid enough to get caught. You think I can spare eight men - or one man - for
that?"

When Rosh coldly refuses to consider his
entreaties to send some men to save Joel, Daniel's eyes are opened. He sees Rosh, whom he had
once idolized, as the cold-blooded, egocentric killer that he is. What Rosh calls "a soft
streak" in Daniel is really a sense of loyalty and humanity, which is essential in a leader
and which Rosh lacks completely. Although Rosh says that Daniel's "softness" and
sensitivity is a fatal flaw, in reality it is a strength. The fact that Rosh lacks this trait is
ironically the fatal flaw in himself (Chapter 18).