So throughout the series Cyon has faced multiple life ending threats analyzing each death in the counter AU hear is the Result

Cyons first kill was GB Cyon, then dark and then we go To infinites army of clones That puts his kill count at an average of 449348, now hears where it gets intresting, Cyon has been to hell in season 4 and 110 billion people had died, lets assume that half of those souls went to hell and became demons, so 55 billion demons also combined with his current kill count is gonna average around 55000449348

Or in short terms Cyons kill count is over 50 billion