Ciaphas Cain facts some heretic Inquisition aides have stated about him and why he keeps winning.
1- Every heretic worships the forces of Chaos, Chaos worships Cain instead.
2- When Abaddon hears Cain is near him, Abaddon runs away in fear.
3- The Tau tried to make machines that could kill Cain, they gave up after researching him for 5 minutes.
4- Trazyn The Infinite said Cain is too much for him, he will collect his corpse instead...after waiting a few years to see if it's safe.
5- Cain kills at least 15 Space Marines with his sword before eating breakfast.
6- Cain was offered a chance to become a powerful Daemon, he decided it was a downgrade and declined.
7- Cain can just walk to Commoragh and make everyone beg for their lives.
8- Cain always know when an Inquisition member is nearby, he just doesn't care.
9- An Ork Warboss looked at Cain once and then ran away to Catachan saying it would be easier to conquer.
10- Death has come for Cain many times now, it's just always ran away at the sight of him.