Continuity mistake: When John goes on the short rampage with the assault rifle we see one of the henchmen climb into an SUV and floor it. It's clear by the hubcaps and rear of the SUV that it's a Ford Expedition, but the vehicle that hits the SUV into john is a Chevy Tahoe. (01:04:00)
Continuity mistake: At the end, John pulls out alongside the two trucks. Camera changes and now he's back in a single line behind the trucks. (01:22:34)
Continuity mistake: When John is chasing the SUV's at the end, he is level with them, then a distance behind them instantly. (01:23:00)
Continuity mistake: When Viggo crashes into John's Charger, it's bent out of shape pretty badly, almost to what would be halfway to the driver's seat. Yet John is fine, and in the next shot, the car is basically too. (01:25:50)
Continuity mistake: At the end, John pulls the knife out of his side and it's got blood on it. Camera shows him starting to thrust the knife into Viggo and the blood has disappeared. (01:27:40)
Continuity mistake: When Viggo dies, he's sat upright. As the camera changes he's now slouched over. (01:29:25)
Continuity mistake: When John's friend enters the room where he is killed he removes his sport coat. When he is tortured and sitting in a chair, his coat is back on.
Continuity mistake: In the night club, when John is fighting the last guy before leaving, the guy throws John, he lands on his back, and has no gun/holster in his waist band on his back. A few seconds later a small pistol and holder appears and he takes it out and shoots at the other guy.
Answer: No. Regardless of any cancellation that Viggo made after-the-fact, the "Cardinal Rule" still applies to Marcus. He accepted the contract, he was contractually-obligated to kill John Wick, and he failed to kill John Wick. Marcus broke his word, essentially, which was an inexcusable violation.
Charles Miller