"It shall bruise thy head" (Genesis 3:15): sounds like a minor skin bruise, like bumping your head

Genesis 3:15 reads, "it shall bruise thy head, and thou shalt bruise his heel." A modern reader thinks of a bruise as a sore purple mark that heals in a week, hardly a fitting punishment for the serpent or a fitting wound for the woman's offspring. The underlying Hebrew word, shuph, is rare in the Old Testament, and its range of meaning runs to "strike," "crush," or "trample underfoot," not a mild contusion.

This is why the verse is often called the "protoevangelium" (first gospel): it pictures a decisive, head-crushing blow against the serpent, even while the serpent only manages to strike the heel. "Bruise" was a serviceable 1611 word for a heavy blow, but English has since narrowed it down to something much lighter, and that shift blunts the force of the promise.