Gotta go fast.
Makkari uses her cosmically powered super-speed to scout planets and as the only deaf Eternal, she is not affected by the sonic boom that accompanies her cosmic running.
Oh wow, now that is a big change from the comics! You can probably figure out simply by the mention of running and super-speed that Makkari is the Eternals' version of Mercury, the messenger god. So that's all the same. In the comics, however? Makkari isn't deaf! He can hear just fine. There's even an issue where he talks about not minding that humans have never been able to pronounce his name correctly, which definitely says he can hear them saying it. So clearly Marvel Studios is okay making changes to suit their actors... at least when we're dealing with absolute nothing characters like the Eternals. Don't expect Chronic Fatigue Wolverine or anything.
Makkari is being played by Lauren Ridloff, who's apparently also in
The Walking Dead. In related news, The Walking Dead is still on. This is one of those instances where the toy was clearly made before the hair and makeup design was finalized, because plastic Makkari has her hair mostly falling free, while the movie shots reveal a single large braid - something that makes sense for a person who would be exposed to tons of wind all the time.
In the comics, "Mark Curry" wears a red costume with white stripes, shoulder pads that would look more at home in the mid-'90s than the mid-'70s, and a big helmet with goggles. Movie Makkari keeps the colorscheme (well, with silver instead of white), but does away with the rest. There are some shoulder pads, but nothing as outré as Kirby drew, and nothing at all like a helmet. There are all the thin, intricate lines that define this movie's costumes, plus a neat little skirt thing that will probably whip around all cool when she's running. You have your choice of fists or gesturing hands: a right hand telling us she loves us, and a left counting to four. Wait... love? Four? Reed and Sue Richarads cameo in Eternals confirmed!
She's also got the right arm and hands of Gilgamesh, the Build-A-Figure.
Makkari is one of the more prominent comicbook Eternals, so it's fitting that she's also one of the stand-out movie Eternals. And changing him to make her deaf seems like a logical addition to the character.