Captain America: Civil War (2016)
Other summer* blockbusters** include Avengers: Age of Ultron, Iron Man (1, 2, and 3), Marvels' The Avengers, Thor, X-Men Originals: Wolverine, Kingdom of Heaven, Spider-Man, The Mummy, Gladiator, Twister, The Fifth Element, Lethal Weapon 3, and Top Gun.
*Summer defined here not by the exact seasonal dates but May through July, generally ("cinematic summer"). **Not only actual blockbusters but movies that the studios hope will be box-office blockbusters.