how to make a villainous main character scary and "aura" without blood or violence?

im writing a main character (also the narrator) who is killing the rest of the entire group of people trapped in an isolated place. i feel like readers getting into this are eventually expecting some levels of power-tripping. the main character is the lowlyest person in the group, and slowly kills the others one-by-one while the rest of the people tries to find out who commited the murders. right now the main character is kind of pathetic and bows down to others--- how do I make the main character scarier, have more "power-triping moments", without describing too much blood and violence?

thanks!