Zack Snyder first entered the realm of superheroes with Watchmen in 2009. He took a graphic novel that was often considered impossible to adapt and made it almost word for word, even adapting panels from the comic in live-action form. One of Zack Snyder's most notable feats is his versions of the Watchmen designs with well-detailed costumes by Michael Wilkinson.
This same designer joined Snyder in creating versions of Batman and Superman in the DCEU. This leads to the question: which Watchmen costumes are the best and which are the least impressive? As great as it was to bring Doctor Manhattan to life, he will not be included due to being pure CGI.
Silk Spectre I
Worn by Sally Jupiter, as played by Carla Gugino, as part of the Minutemen, Silk Spectre sports a short yellow dress with a black corset, large choker, and long boots covering fishnet stockings. It is taken straight from the graphic novel to an almost uncanny degree.
However, in terms of superhero designs, this one is the least impressive seeing how it goes for a more celebrity model look rather than a protector of justice. This fits Sally's character as well as her story but of all the costumes, this one simply just doesn't have as much going for it.
The Comedian Ver. 1
Edward Blake, the catalyst that drives Watchmen, was originally a Minutemen member. During his time with that group as The Comedian, he wore a yellow and purple jumpsuit customized to slightly resemble a clown suit.
It's simplistic but fits the more grounded and realistic superheroes from the Golden Age of comics that Alan Moore and Dave Gibbons were aiming for. It too was taken straight from the graphic novel and fits the Comedian's name along with his twisted view of the world.
Nite Owl I
Of all the original Minutemen, Hollis Mason was the closest to being like a superhero from DC, from the tights to the owl-themed gear to a design reminiscent of how characters were drawn in the 1940s. The first Nite Owl wore tights, an owl-like cowl, and the classic trope of underwear on the outside.
Zack Snyder stuck to this design from the graphic novel well, even managing to make it look like a convincing superhero costume for the brief time it's on-screen.
Nite Owl II Snowsuit
Though it does not get much screen time, Nite Owl II's snowsuit was seen throughout Watchmen. It was there beside his regular suit in the case and was worn by Dan when he and Rorschach go to Antarctica. In the comics, it is depicted as a rather silly white owl covering while the movie version is more akin to an extra layer of suit nearly identical to his base suit.
There are some extra details such as the mask covering his entire face and the furry cloak being portrayed more like a winter trenchcoat. Like the base Nite Owl suit, it is well constructed even if it comes across as a color swap more than anything.
Ozymandias
This one tends to have a mixed response from fans since it deviates almost completely from the novel. Rather than the Egyptian cloth garb like the comics, Zack Snyder's portrayal keeps the Egyptian theme but in a more armored suit akin to what Nite Owl wears.
It's easy to see why devoted fans of the graphic novel might not like it, especially since it features an anatomical design complete with nipples a la the infamously maligned suits from 1997's Batman & Robin. However, on its own, it's much better than those suits and shows a lot of detail that can easily be missed for multiple viewings. Matthew Goode wears the suit well and proves to be an imposing figure in it.
The Comedian Ver. 2
After joining the Watchmen, the Comedian sported a new design wearing an armored vest, metallic shoulder pads colored red, white, and blue, and a domino mask. It fits what he was at that time: a vigilante tool being used by the government and the military. In a way, he was an anti-hero Captain America before John Walker became the anti-hero Captain America.
Since he considered America to be a joke, it also fits his twisted mentality while also giving Jeffery Dean Morgan as Edward Blake a memorable design that was taken from the comics. Although Morgan never wears the leather bondage hood like in the comics.
Silk Spectre II
Laurie Jupiter's suit is a deceptive one: at first, it seems similar to her mother's in that it's more for looks than actual crime-fighting. It's a leather one-piece uniform with high boots that tribute the previous Silk Spectre design while updating it to fit the '80s era.
However, when Laurie and Daniel AKA Nite Owl II get back into crime-fighting, she proves to be an effective fighter and the skin-tight leather outfit with bright yellow pops in the dull environments. Simplistic but effective that helps turn Silk Spectre II into a major improvement over her mother.
Nite Owl II
There are many similarities between Batman and Nite Owl II, one of them is their nocturnal animal designs. The comic book version of Nite Owl II is fine for what Alan Moore was going for, which is why Zack Snyder updated it to be a streamlined armored suit akin to a Batman suit.
From the feather-like patterning of the armor to the billowing cape to the angular cowl, everything about this design fits a modern portrayal of Nite Owl. Patrick Wilson wore the suit well which led to his version influenced the Before Watchmen comics that came later on.
Rorschach
The face of Watchmen (or lack thereof, in this case) is Rorschach. He is a brutal, sociopathic anti-hero but he's the most dedicated crimefighter of the Watchmen. His signature feature is his white mask with a constantly shifting inkblot that reacts to his expressions, movements, and emotions.
Jackie Earle Haley wears the mask along with the famous brown jacket, fedora, and pants to create that iconic noir detective look inspired by The Question from DC. In this case, it was a practical mask used but with a little digital enhancement to replicate the design of the comic and have the shifting inkblots.