Listen to the Stinker Madness Episode
Dirty Harry finally becomes the worst cop in the history of cops when he decides asking questions or arresting people is boring; it's just better to shoot everyone in the face. Sprinkle in some karate, self-deprecating jokes, an unnecessary love interest, old-man grumble dialogue, a car/rc car/car chase, dubious action, and a plot that leaves the audience thinking it was invented by monkeys and you've got the recipe for a franchise killer. Goodbye, Dirty Harry.
The primary problem with The Dead Pool is the incapable hands behind the camera. The script is incredibly dumb, with a "surprise" twist that is blatantly obvious from the first scene in the movie. You're then stuck with a setup for the twist that you're already clued into for the next hour. You know that all the character actions are irrelevant to the actual story and it makes it painful to deal with. So you've got an audience bored with the movie, why not put in another plot as a vehicle for action? Seriously, when your main story doesn't have any call for action, don't add a subplot that is just there so that your protagonist can shoot people in the face. Terrible writing.