Contradiction with Acts 19:5
It mentions believers being baptized in the name of the Lord Jesus, suggesting that Paul did baptize, while 1 Corinthians 1:15 implies he rarely did.
Acts 19:5: When they heard [this], they were baptized in the name of the Lord Jesus.
Contradiction with John 4:2
Although Jesus himself did not baptize, but his disciples, it shows a practice of delegation, similar to Paul's, potentially suggesting more frequent baptisms than 1 Corinthians 1:15 implies.
John 4:2: (Though Jesus himself baptized not, but his disciples,)
Contradiction with Matthew 28:19
This command to baptize by Jesus to his disciples indicates a directive for baptism that may contrast with Paul's claim of rarely baptizing.
Matthew 28:19: Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: [teach...: or, make disciples, or, Christians of all nations]