The question says it all. My choice of course for Alucard. As we've seen is SotN, he can hold his own against the Belmonts if he has to. He can bypass enemies by turning into mist. Plus, unlike the heros who are fully human, he doesn't have to worry about growing old. The only problem is that he is one of a kind and is destined to be alone forever. While he could have a family, he doesn't because he doesn't want to extend his cursed bloodline.