The Midrash in Bamidbar Rabbah 18:22 expounds Iyov 26:12 that when HaShem created the world, he told Rahav, the angel in charge of the ocean, to "open his mouth and swallow all the waters of Creation" to create dry land. The angel refused, saying that "it is enough if I can manage my own," and he began crying. HaShem "stamped" him and killed him, and proceeded to trample on the water and set beaches in place to hold back the oceans such that the dry land would be created.
What was Rahav's complaint? If he was unable to do what was asked of him, that it was beyond his control, then why did HaShem kill him? And if he was capable of doing it, why did he refuse and begin crying?