ULTRAKILL is a game with Rocket-Tag Gameplay. If you don't kill your enemies quickly, they will kill you first. What happens when you can't kill your enemies quickly? You get these guys.
Husks
- Sisyphean Insurrectionists are a perfect example of a Degraded Boss that doesn't feel all that "degraded", only that you the player's skill will have (hopefully) increased by the time you start encountering them as regular enemies. The initial Insurrectionist encountered in 4-2 "GOD DAMN THE SUN" is already That One Boss because it's the first sharp Difficulty Spike in the Act, especially for newer players, but even after that point encountering an Insurrectionist is always an intentionally tough battle. While many of their attacks can be parried, they can very often have extremely wonky timings thanks to their infinite range and habit of constantly jumping a mile into the air, and their extreme weakness to fire damage will only help you so much when they still otherwise have the durability of an Abrams tank.
- Ferrymen have lightning-quick unblockable attacks that deal a ton of damage, are capable of zipping around the arena in a way that makes them dizzying to track, and to top it off several of their attacks are hard to predict or have weird timings. Having to deal with a Ferryman in a crowd of other enemies, especially in a confined space, is a waking nightmare. And of course, because this game is evil, you'll sometimes have to fight more than one Ferryman at the same time.
Demons
- Hideous Masses are relatively easy to kill if you focus them, but the game is wise to this and often pairs them with extremely aggressive enemies in later levels to make focusing on them much harder. And if you don't kill them as the first thing, they'll harass you with extremely damaging artillery fire, and if you're really unlucky immobilize you with their tail harpoon, which is almost always instant death unless you parry it or are right next to them anyway.
- Mannequins are essentially the game's strongest version of its various "standard humanoid low-health" enemies. They move incredibly fast, are more durable than they look, and tend to swarm you from multiple directions at once due to their ability to cling to walls and ceilings. Offensively, they have a one-two punch (a four-punch combo on Brutal or higher) that comes out very quickly and has them get right in your face, and homing blue shots like the Mindflayer which aren't bad normally, but can get out of control when multiple Mannequins are sniping you from different points across the room; it's also somewhat hard to tell whether one is going to try and rush you down or snipe you until it actually begins to attack. Parrying either of their attacks can instakill them, but they'll often scuttle to new positions in between attacks, making them harder to hit with parried projectiles or retaliate against. Furthermore, they have a 50% resistance to explosions, making it harder to cull groups of them at once like you would with most swarm-type enemies. To add insult to injury, their tendency to lie flat and the way their body and gibs look alike can make it look like they're dead when they're really just idle or winded, potentially catching you off guard if you assumed you had killed them.
- Deathcatchers are demonic counterparts to Idols, but much more dangerous. Whereas Idols will pick a single enemy and make them invincible until they are destroyed, Deathcatchers will instead periodically create Blood Puppets of every enemy killed in a given room, from lowly Filths to every other Demonic Spider listed on this page. But if you think you can just Shoot the Medic First, think again, as every Deathcatcher encountered is placed behind an impenetrable glass barrier that will only lower itself once each and every other non-Puppet enemy has been killed. While Blood Puppets are at least weaker than their regular counterparts, any fight involving a Deathcatcher will inevitably devolve into utter mayhem and will overwhelm you if you don't finish it quickly.
Machines
- Mindflayers have an assortment of abilities that make them difficult to fight at any range. They can teleport, fire either homing projectiles or a sweeping laser, and swipe with some strong melee attacks. They're surprisingly bulky despite appearances, and while they have some weak points, they're difficult to hit thanks to their size and their Teleport Spam movements. It's telling that most experienced players say to burst them down with the railcannon and the nailgun before they even get a chance to really get going, and a lot of the fancy tricks you can use to kill them quickly are tough even for veterans to pull off.
- Guttertanks are deceptively speedy and evasive for their size and typically fight from a distance. They'll pelt you with lightning-fast missiles or landmines that will completely throw off your air dashes if not kill you outright with their knockback, the latter of which having a tiny parry window. Within melee range, they have a quick, powerful punch with the same strong knockback as the explosives, and it cannot be parried unless the Guttertank misses and trips over. One Guttertank is already a headache, but they commonly spawn in groups that can easily juggle an unprepared player. And on Brutal difficulty and above, these enemies are even worse to deal with; they don't trip upon missing a punch, meaning they can rapidly follow up on a missed punch with another unless you cover the surrounding floor in the Firestarter Rocket Launcher's gasoline, thus making healing off of their blood extremely risky.
Angels
- Virtues are almost always one of the highest priority threats when one shows up on the field, as they use highly damaging holy beam strikes that can target V1 from anywhere on the map and through cover, which cover a wide area and have lingering hitboxes to boot. Not so bad normally due to their lack of aggression and relative fragility, but in pretty much all cases besides their introduction, Virtues will always appear backing up significantly more aggressive enemies (with multiple at once being a common occurence in later stages), often tucked away in corners of the arena where they'll rain fire from out of sight while you're struggling to handle the other foes, greatly restricting your movement, sometimes even outright being protected by an Idol to make killing them even harder to focus on. On top of that, if you thought you can just ignore it and kill all the other enemies, Virtues will permanently enrage if left alone for long enough and start leading their attacks to make them more dangerous. Like most enemies, they're even more painful on Brutal; not only do they attack much faster, but their beams now only vanish when the next one is fired, turning them from short-lived area denial to full-fledged stage hazards.
- Powers. Have you ever thought to yourself "Gee, ULTRAKILL is so easy! If only Gabriel would follow me everywhere and attack me during group fights, sometimes even duplicating himself through mitosis!" No? Well you can have it anyway, because after 8-3 you get to fight Degraded Boss versions of Gabriel that are exactly as aggressive as him with exactly as difficult-to-predict-and-dodge attacks. Even the fact that they deliberately stop attacking you in intervals doesn't make them any easier to deal with given the hordes of enemies they tend to appear alongside, and unlike Gabriel their attacks are much harder to parry, notwithstanding how parrying their ranged attacks will make them enrage and attack even faster if you don't finish them right away. Powers are on par with Insurrectionists in terms of turning an arena from "already tough" into "nightmare hellscape" as long as even one of them is present.
