The classic mecha-action-cross-psychological-horror anime Neon Genesis Evangelion has a reputation as being a weird sort of show, and it's hard to argue that reputation isn't fully deserved. While it starts out as what seems like a fairly conventional mecha anime, it quickly shows its true colors as a surrealist dive into the nature of being and belonging itself.
That doesn't mean that there aren't any monsters to fight, though. Referred to as "Angels" by the cast of the anime, these mysterious and malevolent beings hail from an unknown place and pursue unknown goals; it's only known that, should they succeed in their ambitions, it would spell disaster for mankind. Fittingly for Evangelion, the physical appearance of many of these Angels is as bizarre as the show itself.
Shamshel
As the second Angel to make an appearance in Evangelion, Shamshel doesn't make quite the impression that its earlier counterpart Sachiel does. There are certainly some elements to appreciate here, however, particularly in regards to Shamshel's primary method of attack; two deadly whip-like appendages that seem to be able to penetrate even an Eva's armor.
It does have a nice color scheme going on, though. With most angels being either black, white, or glowing immaterial masses, it's nice to see that Shamshel decided on purple as the color it was going to appear in when trying to annihilate the human race, and it complements the purple of Eva Unit 01 very well.
Matarael
There's quite a bit going on with Matarael, all of which makes the design pretty compelling. It retains the rigid geometry that made Ramiel so memorable, but this time there's much more of an organic twist. Matarael strides about on spooky spindly spider legs and also sports a prominent orange eyeball that oozes tears of acid.
This is definitely one of the creepier angels to make an appearance in Evangelion. Even if a viewer has a high tolerance for spiders, it's hard not to feel unnerved once this thing starts gushing highly corrosive sludge from its eyeball onto the heads of the Eva pilots.
Gaghiel
Gaghiel leans a little bit further into the "conventional" monster designs that might be familiar to anyone who spends a lot of time watching monster movies or mecha anime; it's a fearsome aquatic beast with a gaping maw lined with hundreds upon hundreds of nasty-looking teeth.
Gaghiel does make an impression as the only fully aquatic Angel the Eva pilots have to engage throughout the series, and the audience can really feel the menace emanating from this thing when its outline is broken up underwater. Seemingly capable of attacking from any direction, Gaghiel's design can easily be filed under the tab of "things one doesn't want to see while swimming."
Lilith
Lilith is notable mainly for lore and story reasons: it doesn't engage the protagonists in combat and is instead held in some sort of captivity on a giant cross in one of the lowest levels of NERV HQ. Lilith plays a decisive role in the plot later on, being a critical component of the many competing agendas that the show's characters are constantly pursuing through subversive means.
When it comes to design, however, Lilith is just plain creepy. This huge, unmoving blob crucified on a hidden cross deep below the Earth suggests some pretty sinister stuff about what exactly is going on behind the scenes with the Eva project and with NERV, in general.
Sahaquiel
Without a doubt one of the largest and strangest Angels in the series, Sahaquiel is essentially an enormous living bomb dropped from orbit with the intent to flatten Tokyo-3 and the members of NERV along with it. Resembling something like a colorful eyeball, Sahaquiel once again upends audience expectations regarding what an Angel can and cannot look like.
Sahaquiel is also interesting because it doesn't seem to have much of a gameplan outside of "fall on top of Tokyo-3," making its choice of attack refreshingly straightforward after so many attempts from the other Angels to drill, melt, or covertly slip into the Geofront to accomplish their nefarious goals.
Leliel
Having already set the precedent for giant floating shapes of death in episode five, Evangelion comes back with another iteration on that theme in the form of Leliel, an enormous sphere with no attack options but the ability to draw an unsuspecting Eva pilot into an alternate dimension like quicksand.
The projection of the striped sphere is not Leliel's true form, however. In fact, the actual matter that makes up the Angel is a non-corporeal substance found in the shadow of the orb, revealing that the orb itself is a simple decoy designed to lure pilots to their doom.
Zeruel
Zeruel is one of the most fearsome Angels in the series on account of its razor-sharp retractable toilet paper arms and its deadly ranged beam attack. Zeruel is able to handily neutralize both Unit 00 and Unit 02 without suffering so much as a scratch, so it's up to Shinji to sort in Unit 01 to finish the fight, though things don't exactly go as planned.
The audience gets an up-close-and-personal look at Zeruel during the battle scene at the end of episode 19, so it's easy to get a good understanding of what makes this Angel feel so menacing. The sheer size of Zeruel is incredible in itself, and, when combined with its bizarre face and deadly arms, it becomes one of the spookiest Angels in the series.
Arael
Arael is one of the scarier Angels in the series, and not just because of the fact that that it's an indistinct being of light that lives in space. While most Angels prefer to use physical attacks and abilities to defeat Evas and gain access to NERV HQ, Arael opts instead for a handy psychological torture beam that it can use to traumatize pilots from geosynchronous orbit.
Arael appears later in the series, episode 22 to be precise, and, at this point, the audience will generally have learned that all bets are off when it comes to the physical appearance of the invading Angels. Still, Arael's behavior and appearance are so different from what the audience is used to that it's bound to be remembered.
Sachiel
As the first Angel to make an appearance in Evangelion's first episode, poor Sachiel doesn't put up much of a fight against Shinji in Unit 01 after it enters a berserk state. Still, it is the first Angel the audience gets to meet, and it makes quite an impression in that regard.
Sachiel's iconic face (or mask?) has become something of a shorthand symbol for the Angels, in general, and, for some, it's the design that comes to mind when Angels are brought up. The Angel itself is an engaging blend of familiar giant monster design elements, but with just enough of a surreal edge to give it an otherworldly vibe.
Ramiel
Ramiel is a fan-favorite in Evangelion circles, and for good reason. The design is sleek and simple, while also being otherworldly and menacing at the same time. Part of the reason that Ramiel makes such an impression in episodes five and six is because, prior to its arrival, the Angels the audience has encountered thus far wouldn't look too out of place in your average kaiju media.
A giant screaming rhombus that fires death rays is a dramatic subversion of the design philosophy that appeared to govern the first two angels engaged in the anime and signals to the viewers that the Angels are far more bizarre and menacing than simple alien invaders.