Contradiction with Numbers 23:19
This verse states that God is not like humans that He should lie or change His mind, while 1 Chronicles 17:26 emphasizes the certainty of God's promise, potentially seen as suggesting a possibility of change.
Numbers 23:19: God [is] not a man, that he should lie; neither the son of man, that he should repent: hath he said, and shall he not do [it]? or hath he spoken, and shall he not make it good?
Contradiction with Genesis 6:6
Here, it states that God regretted making humans, which contradicts the notion in 1 Chronicles 17:26 of God's unwavering promise.
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 1 Samuel 15:11
God regrets making Saul king, which can be seen in contrast to the emphasis on the steadfastness of God's promise in 1 Chronicles 17:26.
1 Samuel 15:11: It repenteth me that I have set up Saul [to be] king: for he is turned back from following me, and hath not performed my commandments. And it grieved Samuel; and he cried unto the LORD all night.
Contradiction with Jonah 3:10
God relents from bringing disaster upon Nineveh, which appears to contradict the certainty of God's word in 1 Chronicles 17:26.
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.
Contradiction with Exodus 32:14
God changes His mind about the disaster He planned to bring on His people, as opposed to the assurance of the promise in 1 Chronicles 17:26.
Exodus 32:14: And the LORD repented of the evil which he thought to do unto his people.