Rashi: I never bore my disgrace. Rather, I stood against him and killed him ¹ .

Rashi (14, citing Menachem): This is connected to "Mi Yiten Li Ever" (verse 7) - if I could fly from Ma'aras Peritzim to the Midbar, enemies would not revile me, and I would not bear shame or need to hide from them. ²

Rashi (14, citing Dunash): It is not an enemy who reviles and I bear shame - rather, it is my teacher, that we would go to Beis Hashem together! It is known that reviling of a lover is harsher to a person that reviling of an enemy.

Radak: Now he discusses Achitofel alone. He was the head advisor. Until now, he loved David and counseled him, until now that he betrayed him. He was not a visible enemy; if my enemy reviles me, I bear it. However, he who appeared to be my lover, and I did not guard from him, how can I bear that he reviles me?!

Malbim: Until now I defeated all my enemies and pursuers, and I bore all afflictions. Now the reviling came from my son; I cannot bear it. I.e. Achitofel had two counsels. (a) Avshalom should have Bi'ah with David's Pilagshim, to disgrace him. Even though he is his son, he must show that he is an enemy to him, so all will know that he is spoiled in his father's eyes; his father will not bear this reproach from his son. (b) To chase David at night. He will not hide in a pit, like Chushai ha'Archi said, rather, he will lodge amidst the people, and Achitofel will kill him at night.

Rashi: When my hater reviled me, I never fled and hid. However, now I am forced to bear my disgrace, for you (Achitofel, who revile me), are great in Torah.

Radak: It is not my hater who inflated his mouth to speak evil against me, that I can hide from him and he will not harm me.

Rashi (14, citing Dunash): One can hide from an enemy, but one cannot hide from his friend, [after] he told to him all his heart!