Thinking about it, I have to say the most impressive thing about Suicide Squad’s make up design (aside from the obvious Killer Croc, Diablo & Enchantress looking amazing) was the transformation of their make up throughout the film.
Harley Quinn goes from having a perfectly painted face to it slowly getting marred and wiped off and drenched as she goes through fights and rain. It has continuity and progression through the film, reminding us that it is indeed make-up she’s wearing. Harley’s face paint runs in the rain. It smudges. Her lip stick smears.
It adds a sense of realism to the film.
And she’s not the only one who goes through this. When Katana takes her mask off, you can see her eye liner and eye shadow smudged from the water.
Suicide Squad did smudged & ruined make up really well, and it’s something you don’t see often in a movie. It’s a really nice touch, and it’s difficult I’d imagine to make messed-up make up still look stylistic and appealing.
Star Trek: Beyond’s alien make up does look good (and it’s very impressive), but it’s also very clean and perfect and we’ve seen it before.
Killer Croc’s make up is every bit as detailed, and that’s in addition to a lot of unique character designs they did for the film from Diablo’s tattoo designs to Enchantress’s dirt and clinging shadows (and later her fully restored form).
(And yes, I do also think that the Joker & Harley’s make up designs were all very well done, varied between scenes and creative whether or not you liked the style, but I don’t think those two are the reason this movie won an Oscar.)
Suicide Squad did a great job with Make Up design, and it’s not an undeserved recognition.