Avengers: Age of Ultron (2015)

The undoubted runt of the otherwise excellent four main Avengers
films is purposeless and a near stand alone mess that almost
interrupts the arc of the other three. Given all involved it is a
surprisingly low-tier entry in to the Marvel movie universe. New
franchise offshoots are set up to little effect and a potentially
interesting artificial intelligence villain story-line is very
muddied, plus the main crew don't really seem to care much this
time out. Winters Soldier is the real fourth Avenger film.