I don't know if even a strict technicality can call Niflheim's army 'human', but I've seen the four of them kill plenty of those.

[Ardyn looked genuinely uncertain of the definition of 'murder' when it came to MTs and the process which created them; Prompto Argentum was one thing, but your average MT was hardly anything living or human in most interpretations of the terms.]

...Apart from that...he's only killed one person that I know of.