Riddle

I am the ultimate killing machine, used not once but twice, I can be made by humans. What am I?

Choose an answer

A.A nuclear bomb
B.A gun
C.A soldier
D.War
Hint: It's a word with 3 letters, starting with "W".

Answer

War

Why this is the answer

This refers to war broadly — humanity has waged World War I and World War II, both devastatingly deadly and entirely man-made.

This riddle is filed under "What Am I?" Riddles and rated Hard.