What is the question "Mah Techashvun"?
Radak: This addresses the enemies, i.e. Anshei Ninveh. What do you think about Hashem, who decrees evil for you? Do you think that He cannot do so, like Melech Ashur said "Ki Yatzil Hashem Es Yerushalayim mi'Yadi" (Melachim II, 18:35).
Malbim: Why do you think bad about Hashem, as if He went out to harm, swallow and destroy? This is not His Midah! His intent is not to harm. Refer to 1:9:2:3.
Why does it say "Kalah Hu Oseh"?
Rashi: He will eradicate Ninveh and the kings of Ashur.
Radak: Know that He eradicates you.
Malbim: Hashem eradicates the affliction, i.e. Malchus Ashur, which afflicted the world.
What do we learn from "Lo Sakum Pa'amayim Tzarah"?
Rashi: He will not repeat to them another time. Radak ? He will wipe them out at once.
Malbim: Via the flood, He will eradicate the affliction, lest it rise again twice. Even though it did rise once after this fall, it will be destroyed again in the days of Nebuchadnetzar. It will not rise a second time.
