"Killer" ability is a special abilty that seems unreal, examples of Speed and Accuracy are shown in the series. It basicly means a genetic superhuman.
To get stronger, they absorb the lives of others, but depending on the number of marks on a Killer, they can absorb that many people).
Hightened or advanced senses (Sight, Hear, Touch, Taste, Smell and Awareness).
Excellent accuracy in throwing projectiles and firing weapons.
Anything to do with physical contact or motion.
Are special type of Killer who were hand made and put a special dice on their forehead which make them able to absorb hundreds of people with ease.