9. Zemo's Mask
After establishing that the Marvel Cinematic Universe had a perceived villain problem over the first two phases, Phase Three began to try and change this. Vulture, Killmonger, and Thanos were among the best the MCU had to offer post-Age of Ultron, as was Helmut Zemo.
Daniel Brühl’s Sokovian antagonist posed the kind of threat the MCU had never seen before, but there was one glaring omission that fans struggled to overlook. You can change his origin, you can make his plan ludicrously convoluted, but how can you bring him to life without his iconic purple mask?
Fortunately, five years after his appearance in Captain America: Civil War, Zemo returned for The Falcon and the Winter Soldier and it was confirmed early on that he would bring with him his trademark headgear. He was seen wearing the mask in the trailer, and it felt right. However, that was about it.
Zemo wore the mask just once throughout the series, with no explanation for why he wore it, what it meant, or any kind of significance. It was pointless and only served to annoy fans even more than before.