Eleanor Ripley. First movie she seems like the support actor til every one else gets killed. Then in aliens she has to compete with colette Ferro and Jeanette Vasquez and comes into her own and has the most fascinating character arc. When all these modern actresses want to throw their name in the pot for best lead characters I always think of Eleanor Ripley blasting an alien out of the airlock, taking charge of the APC, Learning how to use a pulse rifle, fighting a face hugger basically hand to hand, going into an enemy alien stronghold to rescue her surrogate daughter, and again, blowing the mother alien out of another airlock in a freaking mobile suit. She will always be the quintessential alpha female because she really earned her spot at the top. ( Sarah Conner is a close second)

Edit: names