What is the significance of the "Af and Cheimah" of Moshe was afraid?
Rashi (in Bava Basra): They were two tough legionaires that Hashem sent to punish the sinners. 1
How will we reconcile the Pasuk here, implies that Hashem was still angry with Yisrael ("Lehashmid Eschem") during the second set of forty days with the Pasuk in Ki Sissa (Sh'mos 32:14) which states that He had relented already beforehand?
Ramban: Despite the fact that Hashem had already retracted from His initial threat to wipe out K'lal Yisrael, Moshe found it necessary to ascend Har Sinai to Daven on their behalf to protect them against the current wrath and rage of Hashem. 1
Targum Yonasan: When, following the sin of the Golden Calf, Hashem sent down five angels - Af, Cheimah, Ketzef, Mashchis and Charon - to destroy Yisrael, Moshe roused the Avos from their graves to Daven for them. They succeeded in eliminating the latter three, and now, with his Tefilos, Moshe eliminated Af and Cheimah. 2
This refers to other Aveiros for which Hashem thought to destroy Yisrael (in Pesukim 22-23). Refer to 9:22:2:3
This is fine according to Targum Yonason, that "Af" and "Cheimah" are damaging angels -Refer to 9:19:2:2. Da'as Zekenim, Hadar Zekenim, Rosh (all on verse 18) say that Hashem agreed not to destroy Yisrael, but the sin was not pardoned; Moshe now requested pardon of the sin.
Targum Yonasan: Whom he subsequently buried in a pit in the land of Mo'av, by means of the Great Name of Hashem. The question remains however, why do Af, Cheimah and Ketzef Gadol reappear in 29:27?
What does "Gam ba'Pa'am ha'Hi" mean?
Hadar Zekenim: Just like the first time, Hashem agreed not to destroy Yisrael, now He agreed to pardon their sin.
Targum Yonasan: Refer to 9:10:1:2. Just as the first time, Hashem accepted the Tefilos of the Avos and destroyed Ketzef, Mashchis and Charon, so too now did He acept his (Oshe's) Tefilah and destroyed Af and Cheimah.