Suicide Squad/Oscar win
This is just my opinion though and I fully see why people are upset about Star Trek losing to Suicide Squad but I thought id share my opinion on why it did win.
Reasoning: Suicide Squad was by NO means, at all, a great movie. Though they had one of the hardest tasks of all, taking iconic characters everyone knows and bringing them to life in a way that is modern is already a task in itself.
Joker and Harleys redesigns were the most iconic pop culture costumes of 2016, they were EVERYWHERE, their outfits were plastered wherever they could be including their wigs and makeup (there are literally hundreds of makeup tutorials for them on youtube). Everyone dressed up as them and there are thousands and thousands of people who have cosplayed them. Even more so, the designs were so popular they’re now in the comics/video games. I personally don’t like the designs but I can acknowledge how insanely popular they became and still are. Enchantress had a rather unique redesign as well.
Jokers makeup was literally one of the most talked about things last year when they first uploaded that first picture, whether you hated it or loved it it was still being talked about and the press around it was insane.
Killer Croc and Enchantresses minions had wonderful prosthetic work as well and the tattoo applications, while simple, are another thing to look at.
Star Trek had phenomenal prosthetic work for their aliens but it isn’t something the general public are gonna remember/see really after a few months. What you are gonna keep seeing for years to come is people cosplaying the designs from Suicide Squad. It earned its Oscar for being one the biggest Pop culture hits on makeup and hair design alone.