Goofs

When Porter is hit by Pearl and her group of thugs' car, he shatters the windshield upon impact. Several frames later the windshield is completely intact.

When Porter is tied to the chair towards the end of the movie and he is being beaten by Fairfax's thugs there are several shots from behind that show Porter's shoes are on and that his legs are not tied. When Bronson comes and starts to question him these same shots are shown. Before they hit him with the hammer his shoes have been removed and legs tied with no one ever doing this to him.

when Porter gets in the cab with Stegman, the windows repeatedly change from clear to frosted/foggy with every interior/exterior shot of the cab.

When Porter steals the detective's badge, the number on it ends in 86 (the left two digits are covered by Porter's thumb). When the internal affairs detective confronts the detective about his missing badge and shows it to him the number on it is 3887.

When Porter is hit by Pearl and her group of thugs' car he is shown shooting his revolver, usually a 6 shot, 13 times and possibly more off camera, but he is shown actually pulling the trigger and the hammer dropping 13 times in frame.

Porter fires about 40 rounds out of a 6-shot revolver without reloading once.

Porter tells Bronson they will stay in touch regarding the cash transfer. But it remains unclear how. He never asks Bronson for his number. It's though possible that he asks Fairfax or copies it from the phone display after the call. Or he already got it along with Fairfax's data when he checked Carter's address book after killing its owner.

1:13 when Porter puts the badge in Resnicks hand it should have been turned over to see the back of the badge as if it was grabbed from the front.

The frontal views of Porter aiming his revolver clearly show that there are no cartridges in its cylinder.

When Porter and Val smash their car into the Chows' car to rob them, Porter's head snaps forward from the crash, while Val's head doesn't.

When Porter disarms Stegman and beating him up in the back of the taxi, you can see through the frosted glass that the taxi is moving at a really slow speed. Suddenly the driver slams on the brakes and grabs his shotgun but the car isn't moving nearly fast enough to elicit the sound of skidding tires.

When Porter is in the bar talking with the hooker asking where he can find Rosie. The cash on the bar changes front to back several times while the hooker takes the bill from Porter.

When Porter crashes the car into the Chinese Triad's vehicle in the alley, the pre-rigged cable guide system pulling the vehicles together is visible under both cars in the moment after the head-on collision.

While entertaining, an internal affairs investigation would never be conducted in the field as shown. The procedure would involve calling the detectives to the station so the interview could be conducted in a controlled environment and they would have the opportunity for legal counsel.

It makes no sense for either Carter or Fairfax to let Porter kill them just like that. These super rich gangsters could easily have paid him off out of their own personal petty cash without even touching a dime of syndicate money. There was a risk that Porter might kill them anyway but the logical play would have been to at least make him an offer and deal with potential fallout later.

An experienced cop like Leary would know better than to voluntarily leave his fingerprints on an unknown gun. He would surely wipe it before handing it back to Porter.

At 64 minutes, Porter is somehow able to get from his apartment to the assassins' car to cut their fuel line without them seeing him.