Christianity claims that Christ was crucified, died, buried & rose from the dead.
For I delivered unto you first of all that which I also received, how that
Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the
scriptures:
And that he was seen of Cephas, then of the twelve: After that, he was seen of above five hundred brethren at once; of whom the
greater part remain unto this present, but some are fallen asleep.
1 Corinthians 15:3-6
Islam claims otherwise
And for their saying, "Indeed, we have killed the Messiah, Jesus, the son of Mary, the messenger of Allah ." And they did not kill him, nor did they crucify him; but another was made to resemble him to them. And indeed, those who differ over it are in doubt about it. They have no knowledge of it except the following of assumption. And they did not kill him, for certain.
Sura 4:157
At least one of them has to be WRONG