en_tn/1co/15/13.md

if there is no resurrection of the dead, then not even Christ has been raised

Paul is using a hypothetical case to argue that there is a resurrection of the dead. He knows that Christ has been raised and so infers that there is a resurrection. To say that there is no resurrection is to say that Christ has not been raised, but this is false because Paul has seen the resurrected Christ (1 Corinthians 15:8). (See: rc://en/ta/man/translate/figs-hypo)

not even Christ has been raised

This can be translated in active form. Alternate translation: "God has not even raised Christ" (See: rc://en/ta/man/translate/figs-activepassive)