Contradiction with Matthew 10:5-6
Jesus instructs the disciples to not go to the Gentiles, whereas Acts 15:7 involves Peter indicating that the Gospel should be preached to the Gentiles.
Matthew 10:5-6: These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into [any] city of the Samaritans enter ye not:
Contradiction with Matthew 15:24
Jesus states that He was sent only to the lost sheep of Israel, which contrasts with Peter’s claim in Acts 15:7 of preaching to the Gentiles.
Matthew 15:24: But he answered and said, I am not sent but unto the lost sheep of the house of Israel.
Contradiction with Romans 1:16
Paul indicates that the Gospel is to the Jew first and also to the Greek, differing slightly from the specific focus on the Gentiles in Acts 15:7.
Romans 1:16: For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek.
Contradiction with Galatians 2:7-9
Paul mentions that the Gospel for the uncircumcised (Gentiles) was committed to him, while Acts 15:7 highlights Peter’s role.
Galatians 2:7-9: But contrariwise, when they saw that the gospel of the uncircumcision was committed unto me, as [the gospel] of the circumcision [was] unto Peter;