Here’s a good one:
For were it not that the reprobate, through their own fault, turn life into death, the Gospel would be to all the power of God to salvation, (Romans 1:16) but as many persons no sooner hear it than their impiety openly breaks out, and provokes against them more and more the wrath of God, to such persons its savor must be deadly, (2 Corinthians 2:16.)
~ Commentary on Matthew 16:19
So, if it weren’t for the reprobate, universalism would be true. Just a sentence earlier, Calvin states that condemnation is “accidental” to the gospel message, since its essence is salvation. Condemnation comes from a rejection of this message once heard.