R. Yonah: He normally advocates for the way of Sheker, and supports injustice in his dealings with people. He does not recognize the ways of Emes.

Malbim: He switches Emes and the ways of Chachmah to the opposite. "Tahpuchos b'Libo Choresh Ra

Radak: Man's nature is, when one argues with him, he gets angry at unjust words, and shows his own innocence, whether in monetary dealings or verbal arguments.

Rashi: Via his complaint and gripe, he separates the Aluf (Chief) of the world (Hashem) from himself.

R. Yonah: Nirgan makes words or matters opposite, from good to evil, and judges man on the side of guilt and hatred. [Even] a lover and friend, it is inevitable that one cannot find in his words ambiguities that could be explained oppositely. A Nirgan switches from good to evil. Sometimes he adds Sheker to Emes and darkness to light, and covers people's eyes from seeing, until he separates company and love ¹ .

Malbim: Nirgan constantly complains that his colleague hates him and does evil to him. This is like "va'Teragnu v'Ohaleichem va'Tomeru b'Sin'as Hashem Osanu" (Devarim 1:27), "Divrei Nirgan k'Mislahamim" (below, 18:8). He arouses quarrels - "uv'Ein Nirgan Yishtok Madon" (26:20). He separates also [from] a lover and friend who teaches to him the good path, for he says that his friend seeks his evil.