Yet the character is not totally evil, despite being responsible for the deaths of those staying in his house. His reasons for doing this were to try to help save someone he loved and the story is both tragic and gripping.
The Doctor interestingly does not just condemn the Landlord character (as he so often does with those characters who are just evil for the sake of it - i.e. the Daleks!). Indeed it is clear the Doctor can see exactly why the Landlord has done what he has but that it has to stop and indeed the Doctor forces the stop. Brilliant performances all round and excellent writing. Truly convincing characters.
And that is what to aim for with all of our characters, whether they are evil, good or a mixture. Their motivations must be powerful and realistic enough to convince your reader yes someone really would be like this for the reason(s) given.