During an overseas chavrusa, the question arose: HOW COME THE BROTHERS NEVER REGRETTED THE SALE AND MISTREATMENT OF YOSEF?? All they said was that they were guilty for not having mercy when Yosef begged them not to throw him in the pit but not on what they actually did:
The Mekubalim say that the עשרה הרוגי מלכות were gilgulim of the brothers who were punished for what they did. In fact, we never see that Yosef actually forgave them [maybe because they didn't ask...]. Why didn't they??