Great movie but...
Seven has a lot going for it, great cinematography, wicked plot, good cast, but it would have made it a better movie in my opinion if John Doe didn't have to resort to killing an innocent person in order to complete his "masterpiece".
His fierce defense in the car when he gets accused by Mills of killing innocents falls really flat considering he did kill someone who was innocent.
Beside, I don't think Mills demonstrate such a huge uncontrollable anger throughout the movie that he would deserve to be punished for it. Actually I imagine tons of people far more subjected to uncontrollable anger than him. That's also another downside in this movie.
John Doe shows little consistency in his choice of sinners and also his ways of torturing/killing them. Being a "sloth" sinner results in such harsher punishment than being a "pride" sinner that it makes the "masterpiece" utterly lack cohesion and just seems very random.
So it's a great movie no doubt about that, but the "mind" of the killer as depicted in the movie is far from as great as they would like us to believe, in my opinion.