1)
What is "Shofetenu"?
1.
Rashi: He is our officer and judge.
2.
Radak: He will judge us against Melech Ashur. He will wage our case against him; he did many evils to us.
3.
Malbim: He brings the river water (Melech Ashur) against us due to our sins.
2)
What is "Mechokekenu"?
1.
Radak: He rules over us. A ruler us called Mechokek - "u'Mechokek mi'Bein Raglav" (Bereishis 49:10), for he makes Chukim (laws) in the nation. Kel is our judge, lawmaker and king - He will save us!
2.
Malbim: He makes the laws; He can change them as He desires.
3)
Why does it add "Malkenu"?
1.
Malbim: He can pardon the sin like a king, who can go beyond the letter of the law. If so, He will save us.