What was the fear?
Rashi: They will fear at the end of days (refer to 14:5:1:1).
Metzudas David: When Sancheriv camped against Yerushalayim, they feared in Yerushalayim.
Malbim: Refer to 53:5:4:2.
Why does it say "Lo Hayah Pachad"?
Rashi: This fear will not be like the fear in the days of Belshatzar. [Rather, it will be greater -] "Hamek Besaro
What is the meaning of "Elokim Pizer Atzmos Chonach"?
Rashi, based on Menachem: Hashem will scatter the bones of those who camp against you, Yerushalayim. Radak - it says about Yerushalayim "u'Va Hashem Elokai Kol Kedoshim Imach" (Zecharyah 14:5).
Rashi citing Dunash: "Chonach" is like "Chanoch l'Na'ar Al Pi Darko" (Mishlei 22:6). The Chaf is part of the root.
Radak: Hashem will scatter the bones of those who camp against you, Yisrael. Also when Mashi'ach comes, they will plot to kill him and nullify his kingship. "Va'Yetzei Hashem v'Nilcham ba'Goyim ha'Hem" (Zecharyah 14:3).
What is the meaning of "Hevishosa Ki Elokim Ma'asam"?
Rashi: You (Hashem) shamed all my enemies, for You despised them.
Radak: The suffix Sov in "Hevishosa" refers to Mashi'ach. He shamed them and made their pride shame for them, for Elokim was with him.
Malbim: [He scattered their burned bones. They will not be gathered or buried,] for Hashem despised them.