1 Corinthians 1:23 (NIV)
We preach Christ crucified.
All world religions accept that Jesus was a good teacher and a noble man. The difference between Christianity and other world religions is that we believe that Christ was actually crucified for our sins. As Paul puts it, the crucifixion is a stumbling block to the Jews who claim that Jesus of Nazareth was a common criminal and foolishness to the Gentiles who have no faith. Had Christ not been crucified there would have been no atonement for sins and Christianity would have been just another feel good religion. The cross of Christ defines who we are and sets us apart from unbelievers.