Why does it say "Ach Elokim Yimchatz Rosh Oyvav"?
Rashi: [Hashem has ways to lead to many kinds of deaths - not for us, rather,] to crush His enemies' heads.
Radak: Elokim alone will do this. Who can do like His Ma'asim? At night, in one moment, he struck 185,000 1 men. Only Elokim can strike the heads of his enemies without a sword or spear!
Malbim (21-22): [Since the angel of death does not come to Eretz Yisrael,] Hashem Himself will crush their heads.
What is the meaning of "Kadkod Se'ar Mis'halech ba'Ashamav"?
Rashi: The head of Esav, who was "Ish Se'ar", always goes in his sins (he does not repent). Malbim - i.e. the heads of Bnei Edom. They did not die in Bashan naturally, rather, miraculously via Hashem.
Radak: Kadkod divides the hair - half is to the right, and half is to the left. Because Kadkod is the end of the head, it says about decrees that descend on a person, good or bad, Kadkod, e.g. for Brachah "ul'Kadkod Nezir Echav" (Devarim 33:16), and for evil "v'Al Kadkodo Chamaso Yered" (above, 7:17). [Hashem will crush] Kadkod of one who goes in his sins and does not repent.
