Continuity mistake: It was briefly stated in the second film that the T-Virus was created by Dr. Ashford to cure his daughter Angela and that the Red and White Queens were based on her. This movie contradicts that by suggesting that Dr. Marcus created the T-Virus to cure his daughter Alicia, and that the Red/White Queens were modeled after her. While the rest of the movie stays true to the continuity of the previous films, this rather obvious ret-con is still a major continuity gaff.
Continuity mistake: There is a scene of Alice being dragged by a line behind Isaacs' tank ahead of a horde of zombies. There is no other line next to running Alice. When she climbs upon the tank to attack the guard, another line with torn hands is seen being dragged on the road, where Alice was dragged.
Other mistake: Alice is running behind the armored cars. Once she manages to get on top of the car, suddenly the zombies that were only behind her and nowhere near the car are found at the sides too, attacking a guard and later Alice as well. Not possible considering if zombies were able to get there, they would have killed Alice while she was running.
Trivia: Every previous film ended with a dramatic zoom-out starting with Alice that teased the events of the sequel that followed. Appropriately, "The Final Chapter" ends by doing the opposite - dramatically zooming into Alice and ending with an extreme closeup of her eye. This also bookends the series, as she was introduced in the first film with an extreme closeup of her eye opening.
Trivia: While the film had the lowest domestic gross of the series ($26 million in comparison to the $40-$60 million each other film grossed), it was somewhat ironically also the highest grossing film of the franchise internationally, and as a result also ended up being the highest grossing film of the series worldwide, earning $312 million against a $40 million budget. It serves as a rare example of a film that is a flop in domestic markets while still technically being a resounding success.