There is a small genre of sci-fi short stories in which humans turn out to be the scariest species in the galaxy due to our possession of apparently mundane abilities. For example:

• Human muscles have the terrifying ability to become increasingly more massive and powerful when placed under a routine of extreme stress. Many humans systematically overload their muscles in this way. For fun.

• Humans breathe oxygen, a component of starship fuel!

• The brain of a human is protected by an armored skull so powerful that a human fighter is impervious to any simple attack to the brain and can even use its braincase as a weapon to bludgeon enemies.

• Humans naturally produce dangerous hormones and stimulants such as epinephrine. In desperate situations these boost a human's abilities, allowing it to continue functioning even when severely wounded.