Contradiction with Proverbs 16:9
This verse suggests that the Lord directs the steps of a man, while Acts 12:10 describes an angel leading Peter, which could imply a secondary agent rather than divine direction.
Proverbs 16:9: A man's heart deviseth his way: but the LORD directeth his steps.
Contradiction with Matthew 28:2
In this verse, an angel causes an earthquake when rolling back the stone from Jesus' tomb, displaying power, whereas, in Acts 12:10, the angel leads Peter silently past the gate without disturbance.
Matthew 28:2: And, behold, there was a great earthquake: for the angel of the Lord descended from heaven, and came and rolled back the stone from the door, and sat upon it. [was: or, had been]