Contradiction with 1 Samuel 18:20
It contradicts 1 Samuel 18:19 because it states Michal, Saul's daughter, loved David, whereas 18:19 speaks of her being given as a wife to Adriel instead of David.
1 Samuel 18:20: And Michal Saul's daughter loved David: and they told Saul, and the thing pleased him. [pleased him: Heb. was right in his eyes]
Contradiction with 2 Samuel 21:8
This verse contradicts 1 Samuel 18:19 by referencing the sons of Michal, suggesting that she was married to David and not Adriel.
2 Samuel 21:8: But the king took the two sons of Rizpah the daughter of Aiah, whom she bare unto Saul, Armoni and Mephibosheth; and the five sons of Michal the daughter of Saul, whom she brought up for Adriel the son of Barzillai the Meholathite: [Michal: or, Michal's sister] [brought...: Heb. bear to Adriel]