What do you think would be a good twist for my novel?

I honestly really like it. However, what might be even better is, if the the drug dealer killed the lawyer already by the time Leon gets there and it was the drug dealer's plan to frame Leon. He convinces Leon he has to kill this guy, and Leon gets there, with the murder weapon and everything and the cops have been tipped off anonymously and catch him, practically in the act. What if it was a set up from the very beginning? Something to consider. The most important part, however, is that you understand the story, characters, scenarios, and such. The quality of you writing will depend on that, so write what you're most comfortable with, so you can really bring the reader in and create a story worth finishing.