Possible meanings are 1) "condemn" here represents accusing. Alternate translation: "and will accuse this generation of people" or 2) God will condemn this generation of people because they did not repent as the people of Nineveh had. Alternate translation: "and God will condemn this generation" (See: [[rc://en/ta/man/jit/figs-metonymy]])
You can make explicit the implicit meaning of Jesus's statement. Alternate translation: "than Jonah is here, yet you still have not repented, which is why God will condemn you" (See: [[rc://en/ta/man/jit/figs-explicit]])