People who enjoy killing are most likely psychopaths but other
then that there are no speical words for someone who likes to
kill...well I guess you call just call him a ruthless cruel person
with no regards of human life a or maybe Misanthropy (a person who
hates humans)
A person who enjoys killing is commonly referred to as a "murderer" or a "serial killer." These individuals have a deep-seated psychological issue and often lack empathy towards their victims.