Who is the Worst Person in Memento?

The film adataption of the story is a confusing, tangled story of revenge. Every character has some good and bad in them. Is Teddy/John G (Joe Patoliano) good for helping a wronged man seek out revenge and peace of mind? Is he wrong for using Leonard (Guy Pearce) and his condition to kill bottom feeding criminals that would merit little investigation into their death. He is serving as a guide for Leonard at the same time he is profiting off of using Leonard as a murder weapon. If he wasn't using Lenny to kill drug dealers, if he wasn't trying to help Lenny gain a sense of accomplishment, would they have crossed the path of Natalie (Carrie-Anne Moss?) A woman who has her lover taken from her by means of murder at the hands of Teddy and Lenny.
Does Natalie realize how much she and Leonard have in common? Both had the object of their affection taken from them brutally, both seek out revenge by whatever means. Does Natalie realize how much she has in common with Teddy when she sets out to help Leonard find John G; the murderer of his wife? Does she believe that Leonard is going to kill the man that ruined his life, or the man that ruined hers?
Though these two use manipulation in a good-hearted way, Leonard chooses to live in self decpetion by the end/begining of the movie. He ignores the truth, that he has killed at least one man if not several, that the man trying to resolve his mental block is now the target Leonard chooses to collect facts about. He relies on his condition to erase the memories he doesn't want, and create a life where he has purpose.
The short story was excellent in my opinion, pieces of it coming together like flashes sell the effect of short term memory loss. The theme that keeps comgin back to me in the movie though is self decpetion. Teddy/John G. deceives himself into thinking it's okay to let Lenny kill random men. Natalie deceives herself into thinking making Leonard kill Teddy/John G. will exact revenge for losing her lover. Leonard deceives himself into thinking he is someone who is long gone. Once an insurance claims investigator, now a roaming killer with a mental disorder.