The film's most used tagline is, "You won't believe how it ends." Visit the IMDB message board for the movie, and you'll see that a lot of people are crying foul, saying that they saw Hoffman's framing Strahm coming a mile away. That's not what the tagline is referring to. Think of how the movie ends; Strahm ends up crushed - pulverized, even - by the closing walls. How many Saw films before Saw V showed such a trap (hell, even Star Wars had it!), but how many of those films showed every single fucking detail of the final result? You won't believe how it ends indeed!
Also, the poster with that tagline has a surreal image of a man wearing a mask featuring the face of John. According to the marketing team (and contrary to popular belief that it's Hoffman), this man is supposed to be Strahm. As some Reddit users from the subreddit for the franchise have pointed out, the poster is a symbolic image of Strahm's fate: at the end, he dies and is framed in death as the new Jigsaw by Hoffman.
Another thing: The scenario of Strahm's death is a The Walls Are Closing In scene. Normally, in movies using this, the protagonist usually finds a way to escape. Here, however, Strahm doesn't escape, and he's Squashed Flat. The director David Hackl said that he wanted to see a scene of such type where the person doesn't survive.
When John captures Hoffman, he berates him for his “inferior work”, and specifically criticizing Hoffman’s choice of metal for the pendulum blade that killed Seth Baxter, saying that he personally uses tempered steel for his blades, as it holds an edge better; dull blades actually leave worse injuries than sharp blades, as they rip and tear the flesh in more traumatic and irreparable ways. John puts his victims through torture to rehabilitate them, but only puts them through pain until they escape. In John’s eyes, Seth had won his game by crushing his hands and his brutal demise with a poorly-made blade that probably made his death more painful is not only an insult to his philosophy, but also an insult to the care he puts in his work.
, the poster is a symbolic image of Strahm's fate: at the end, he dies and is framed in death as the new Jigsaw by Hoffman.