Mary
Genesis 3:15
I will put enmities between thee and the woman, and thy seed and her seed: she shall crush thy head, and thou shalt lie in wait for her heel.
Context of the passage
Immediately after the Fall, God curses the serpent and foretells the ultimate defeat of evil by the offspring of 'the woman,' the Protoevangelium, the first Gospel promise.
Catholic reading
The 'woman' whose offspring crushes Satan's head is understood typologically as Mary, the New Eve, standing in perpetual enmity with the serpent, which the Church sees as pointing toward her Immaculate Conception, being free from Satan's dominion from the first moment.
Common objection
The 'seed of the woman' refers collectively to humanity or specifically to Christ alone, not to Mary personally.
Response
While Christ is the primary 'seed' who conquers Satan, the text names 'the woman' herself as the one in enmity with the serpent, and since Mary is the immediate, literal mother of that decisive seed, her singular role is naturally implied within the same prophecy.
The Church Fathers
“Eve... having conceived the word of the serpent, brought forth disobedience and death. But the Virgin Mary... answered, 'Be it done unto me according to thy word.'”