(at around 2h) Throughout the entire car chase scene in Paris, John car hits multiple other vehicles and people. Yet, except for the missing doors and windshield, there's not a single dent anywhere on the car.
(at around 2h) When John is thrown into a Mercedes minivan during the Arc de Triomphe shootout, the driver is never shown leaving the minivan. But in the next shot, no one is inside. Also, the lights were on when John was thrown, but in the next camera shot, the lights were off.
(at around 2h 10 mins) When John is fighting the Tracker on his way to the duel, sunlight is streaming through the building windows (in which they are fighting). Yet when he busts through a window and falls to the street, it is still completely dark out.
(at around 2h 10 mins) After jumping off of the building right before the final stairs fighting scene Wick checks his watch and reveals that it is 6.18 am. Seconds later in the foot of the stairs he checks his watch again and it is 5.55am.
(at around 2h 5 mins) When John is running around Paris the night before he meets The Marquis for the duel, he enters a closed building, which just happens to have all its lights off, and its front doors unlocked. He then is seen busting open one set of double doors. The bad guys that follow him have to again bust open both sets of doors, of which at least the second interior French style doors would still be open from John's passing.
(at around 47 mins) Caine can aim and shoot at people using his hearing but fails to hear Wick breathing heavily 2 feet from him.
(at around 56 mins) Japanese train, lights never go down even while running and also the seat is made of fabric instead of plastic.
(at around 2h 5 mins) Dragon's breath rounds can't be used in semiautomatic shotguns, due to not producing enough recoil to cycle the action, and don't light people on fire nearly as easily as they do.
(at around 2h 15 mins) When Caine meets John at the stairs, he asks " how long until sunrise?" John says "Two minutes. Maybe three." The fight up the remainder of the stairs takes over four and a half minutes. The sun was late for work that day.
(at around 1h 13 mins) Killa's night club in Berlin appears to be some multi-story Greek temple. Its actually the Alte Nationalgalerie on Museum Island which hosts several pieces of priceless German art and definitely does not have torches and a three story indoor rain fountain.
(at around 2h 15 mins) During his night fight in Paris, John never reloads his 9mm Viper pistol despite firing more bullets than the 21 round magazine can hold. He reloads as he is rejoined by Caine after being kicked down the stairs in Montmartre.
(at around 1h 50 mins) "The Paris Continental's radio station has the call sign "WUXIA". The use of lettered "W-" or "K-" call signs on commercial radio is a uniquely American thing; a French radio station would instead identify itself by its formal name or a radio frequency. They also generally only have four letters." However, the call sign is a homage to Wuxia, a genre of Chinese fiction involving martial artists in ancient times.
(at around 2h) The Arc de Triomphe is missing the eternal flame which crowns France's Tomb of the Unknown Soldier. As its name suggests, it is never ever allowed to go out.
Typical Hollywood action movie henchmen "waiting" for their turn to be hit by Wick, instead of going all at once.
In one scene, you can see the skyline of New York from Queens, and everything is proper except One World Trade Center, which is between the Empire State Building and the Chrysler Building, as well as the Citigroup Center, when One World Trade is miles south in southern New York City.
(at around 6 mins) In the opening scene, after galloping through the desert on horseback and shooting The Elder, John Wick, wearing a black suit, shows not one drop of perspiration.
(at around 37 mins) Obvious retractable blades when the female fighter stabs the henchman's back with her knives (they move around while she tries to hold still on his back).
Even though there is a prolonged gun battle through the streets of Paris, not a single police officer is seen or siren is heard to respond to the chaos.
If Wick's "plot armor" suit is indeed made of Kevlar, it should be about 2 centimeters (0,8 inches) thick to stop all rounds fired at him. It would also be stiffer and weigh like a normal bullet-proof vest, being very cumbersome to wear.
(at around 1h 50 mins) The presenter of the Parisian continental radio station should be presenting in French, seeing as the listeners are all French.
During both the club and Arc de Triomphe scenes, civilian dancers/drivers clearly see the violence, including multiple people being shot and killed, yet continue to go on normally.
(at around 48 mins) When his contract was increased to 20 million USD, the German female accountant says "John Wick, vertraglicher Anstieg auf zwanzig (20) Milliarden Dollar", meaning 20 billion USD, with a B.
(at around 19 mins) When the Tracker checks in to the Osaka Continental with his dog, Tracker refers to himself as being HER emotional support animal, implying the dog is a female. But when the dog pees on Chidi after Tracker kills him (at around 2h 20 mins), the dog lifts a hind leg the way a MALE dog pees. A female dog would have squatted.
(at around 4 mins) Wick has the greatest difficulty killing the horseback riders when aiming properly but then suddenly kills the second one (who is in front of him on his left) without even aiming and with his right hand behind the horse's head (his gun was pointing right less than a second prior in the previous shot).