Cavil blackmailing Ellen Tigh into sleeping with him was grim enough, but the Final Five's backstory made their tryst more sickening than initially thought.

Source: https://screenrant.com/battlestar-galactica-final-five-cylon-twist-problems/

In the final weeks leading up to the attacks, multiple copies of John Cavil circulated among the Colonies, ensuring the progress of their diabolical plans.

Source: https://gamerant.com/battlestar-galactica-fall-twelve-colonies-explained/

Tory Foster miraculously survived a blast near Delphi, and though seriously injured, Ellen also survived an explosion on Picon, with Cavil, interestingly, aiding her rescue.

Source: https://gamerant.com/battlestar-galactica-thirteenth-tribe/