What is the enemy's voice?
Radak: I hear that the enemy, i.e. Avshalom, wants to expel me from kingship and kill me. I mourn also due to Bnei Yisrael who conspire with him.
Malbim: They speak about me words of hatred and disgrace.
What is "Akas"?
Rashi: It is an expression of Matzok (distress).
Radak: It is affliction.
What is the meaning of "Ki Yamitu Alai Aven"?
Rashi: Do'eg and Achitofel are Machri'a 1 against me sins, to show that I am Chayav Misah, and they permit [to spill] my blood.
Radak: They lean against me Sheker. They rebel against me and lie about their integrity, that they made me king over them with a full heart. Now they hate me with anger, and they established my son against me!
They make that side of the balance scale go down. (PF)