Continuity mistake: In the final battle, Wasp and Ant-Man are in the van trying to get the quantum tunnel operational. We cut back to the fight and we can see Ant-Man there too, fighting in his giant form. (02:22:20 - 02:23:00)
Factual error: It is not possible that Pitt could have gone up to the ship when it was already blasting off. There was literally fire in the tunnel.
Continuity mistake: After the speeder chase, everyone lands in quicksand. In one shot, 3PO is buried headfirst. In the next, he has flipped and his upper body is visible.
Factual error: The space shuttle is spinning due to a stuck thruster. In such a case, the spin would be continually increasing as there is no air resistance. The X-Men shoot out of the thruster and the spin stops. Not factual. They would have needed opposite thrusters to stop it. (00:11:55)
Plot hole: Sarah turns up on the bridge to fight the Rev-9, we later learn that she is texted the location of where to be as when the terminators travel though time it causes a gravitational anomaly, and this is where she needs to be. The Rev-9 had been there ages killing Dani's dad etc, Sarah would have no idea to be on the bridge after the terminator has chased them though the town - she can't possibly know that location.
Continuity mistake: When Peter and MJ hug on Tower Bridge he gets some blood from his face onto the left shoulder of her jacket. From other angles there's no blood.
Revealing mistake: A major selling point of the movie is the CGI technology used to de-age Will Smith. The effect works for the most part of the movie, including scenes in daylight, but in the last handful of minutes, maybe because of the plain 'happy-ending' light used, maybe for budget reasons, the face of Junior is thoroughly unconvincing, with a dramatic drop in quality in textures and modelization. (01:44:30)
Revealing mistake: In the beginning of the movie, when Hellboy is speaking on the phone with "Dad", he's speaking on on speaker, but when the phone shows up, instead of showing a screen of a call on speaker with the duration on the call, the screen shows what would appear if he was receiving a phone call before accepting or declining. (03:35:00)
Plot hole: Spoiler. Agent M points out as highly suspicious that the twin assassins knew the location of Vungus, and High T backs her up on this, saying that only a handful of MIB officers could have leaked that information. High T also established that those aliens were part of the Hive collective. It turned out that they were not part of the Hive, and the Hive connection was made-up entirely by the villain himself...which is the Hive! What he did was absurdly counterproductive to his cause: nothing except the report he himself made up connected the Hive at all with the case.
Continuity mistake: After Brandon finds out he arrived in the alien craft, he walks outside in the rain where he finally translates "Take The World" as his purpose. He continues on to Caitlyn's house to tell her what he has discovered and to give her a flower. When he arrives in her room, he is completely dry.
Continuity mistake: Dr. Stone mentions there is an emergency exit below the landing pad. He then asks the pilot if there is a camera underneath. In this shot, the pilot has his eyes partly closed and his lips pursed together. It cuts to a close up of him and suddenly his expression is different, with his eyes wider open and his mouth open. (00:19:50)