Walter is the butler and right hand of Integra Hellsing. He has served 3 generations of Hellsing family members, and in Integra's eyes, her most loyal servant. He is a kind man, who cares about his master and Seras deeply. He has a long term friends with Alucard, since they have know each other ever since Walter was a young boy.
Walter may be an old man now, but he is still a lethal fighter. Alucard refers to him as "the Angel of Death", a name Walter earned when he was younger. He uses wires to slice his enemies into pieces, literally. He is a kind and gentle man, but he is also capable of incredible cruelty and ruthlessness towards his enemies. All and all, he is one old man you don't want to cross.