This is difficult. I do remember reading in a book about St. Thomas Aquinas about the crusaders that were captured by Jihadists. They were required to convert or die.
To convert to Islam, one says the shahada or islamic creed in Arabic: I bear witness that there is no God but Allah and Muhammad is his Apostle"; in Arabic “Ash’hadu n la ilaha ilallah, wa ash’du wa Muhammadar Rasul’ulah”
So the crusaders would say in unison the first part “there is no God but God” but in the second part would mumble jibberish that sounded like the phrase “Muhammadar Rasul” but wasnt and then say the last part “LULAH!” very loudly.
Essentially, they lied that they had renounced the faith.
The Romans knew to catch Christians not just by asking them to make statements that would mean renouncing their faith, which many did verbally and then later repented, but by having them insult and curse Christ himself.
They figured out that no one who truly believed that Christ was divine could bring themselves, at least not easily, to curse him, while very many could easily pretend to renounce their faith just to escape death. They caught many Christians this way.
Of course many must have still cursed Christ, but can you imagine how difficult it is for someone that believes in Christ to hurl curses at him? It is easier to simply lie and say “I don’t believe in him” like St. Peter did, out of fear of death. But having a true Christian hurl pervated or other unspeakable curses at Christ is difficult even for an average Christian, they don’t have to be saintly. Those Romans were very cunning.