What is the meaning of "Mi Yode'a Oz Apecha"?
Rashi: In these few days, who will acquire a heart to know the strength of Your anger, to fear You?
Radak: Who can be guarded from Your anger? How strong is Your anger!
Malbim: We 'fly' with the flow of time; we cannot know the strength of Your anger, that You will punish us for individual sins - "Ki Chalinu v'Apecha" (verse 7).
Why does it say "uch'Yir'asecha Evrasecha"?
Rashi: Just like You are feared, so Your anger is harsh, and punishes sinners.
Radak: The more that one fears You, there is more anger against him when he sins a little. This is like Moshe said about himself "va'Yis'aber Hashem Bi Lema'anchem" (Devarim 3:26). Hashem would not have guarded (punished for) such a sin from someone else. He said about Aharon's sons "bi'Krovai Akadesh" (Vayikra 10:3).
Malbim: No one can know Your general anger for Adam ha'Rishon's sin. It resembles the great fear of You. It includes all living beings; all die due to that anger.