Andrew Bennett is a 16th century noble who fell in love with one of his maids, Mary Seward, as he was on his way to flee with her from his father he was bitten by Cain, the first Vampire, becoming the Demon Lock, destined to be the seal protecting the world from Cain's influence. He later turned Mary into a vampire, but unlike him she couldn't control her bloodlust, becoming Mary Queen of Blood. Andrew then spent the next 500 years fighting vampires and other mystical influences.
During the 21st century, Bennett is wounded in conflict with Mary and seeks aid from his old ally Professor Troughton. Together with the young vampire hunter Tig and the vigilante Batman, the group confronts Mary at her lair. Tig kills Bennett, and Cain is released from his magical prison. Justice League Dark attempt to hold back the horde of vampires commanded by Cain until Madame Xanadu revives Bennett. Bennett kills Cain and assumes command of the vampires, vowing to maintain a period of peace and nonviolence between vampires and humans.
Battle vs. Alucard (Hellsing) (by LokoDito)
Both vampires are really super tough and all-powerful, but Alucard lacks any way to actually damage Andrew Bennett, while the latter has an assortment of magical powers which can actually affect Alucard. Even if the battle does not end to the death, it is believed that Bennett has the skills and cunning to outsmart Alucard who mostly uses brute force.