Species II (movie, 1998)

Having just returned from a mission to Mars, Commander Ross isn't exactly himself. He's slowly becoming a terrifying alien entity with one goal -- to procreate with human women! When countless women suffer gruesome deaths after bearing half-alien offspring, scientist Laura Baker and hired assassin Press Lennox use Eve, a more tempered alien clone, to find Ross and his brood. Before long Eve escapes to mate with Ross.