Avengers: Infinity War made a big fuss over bringing in The Black Order from Jonathan Hickman's Infinity event, where they were revealed as some of Thanos' best henchmen. Honestly, making them Henchmen was a bit of a mixed bag since they were never the most interesting characters in the comics but they did have some depth and intrigue that were ignored for the movie.
Though they never made much of an impact in the MCU, aside from a few cool fight scenes, Avengers: Endgame almost made one of them important. Well, more important than what we saw during the movies anyway.
Proxima Midnight actress Carrie Coon revealed that she was actually called to record some dialogue for Endgame but wasn't able to because of scheduling issues. In the end, Monique Ganderton ended up taking the Proxima Midnight role in Endgame, though they didn't have her speak any meaningful dialogue, unfortunately.
Considering what she told Entertainment Weekly, one has to wonder what Proxima Midnight would have said in Endgame. The characters ended up just being used for more cool fight scenes and not much else during Endgame, while most people only remember her mocking Scarlet Witch for "being alone" in Infinity War.
Most comic book fans know that The Black Order is a little more interesting than what these films showed but we can't blame them for their roles. After all, movies aren't allowed to have the depth of a television series or even a comic book so that's just the reality we have to accept. If previous recastings are anything to go by, she could always be recast for a cooler character in the future.
Avengers: Infinity War and Avengers: Endgame are now available for viewing on Disney+ or through Blu-Ray, assuming you've purchased it.