Contradiction with Genesis 6:6
This verse states that God repented for making man, contradicting the concept of God's enduring faithfulness across generations.
Genesis 6:6: And it repented the LORD that he had made man on the earth, and it grieved him at his heart.
Contradiction with Jeremiah 18:7-10
These verses suggest that God can change His mind based on human actions, which can be seen as inconsistent with the steadfastness implied in Psalms 119:90.
Jeremiah 18:7-10: [At what] instant I shall speak concerning a nation, and concerning a kingdom, to pluck up, and to pull down, and to destroy [it];
Contradiction with 1 Samuel 15:35
God's regret in making Saul king implies a changeability that contrasts with the enduring faithfulness described in Psalms 119:90.
1 Samuel 15:35: And Samuel came no more to see Saul until the day of his death: nevertheless Samuel mourned for Saul: and the LORD repented that he had made Saul king over Israel.
Contradiction with Jonah 3:10
God's decision to spare Nineveh after they repented shows a change in His action, which could be seen as a contradiction to the unchanging nature suggested in Psalms 119:90.
Jonah 3:10: And God saw their works, that they turned from their evil way; and God repented of the evil, that he had said that he would do unto them; and he did [it] not.