Specimens (Killing Floor 2)

The Specimens, also called ZEDs, are the main enemies of Killing Floor and Killing Floor 2. While they are sometimes referred to as zombies, they are, in fact, super-soldier clones created by bioengineering company Horzine Biotech's ex-CEO Kevin Clamley, now known as The Patriarch. There are total of 21 different specimens in Killing Floor 2:

6 lesser ZEDs (Cyst / Alpha Clot / Slasher / Stalker / Crawler / Gorefast)
4 medium ZEDs (Bloat / Siren / Husk / E.D.A.R)
3 large ZEDs (Quarter-Pound / Scrake / Fleshpound)
3 elite variants (Rioter / Elite Crawler / Gorefiend)
5 bosses (Dr. Hans Volter / Patriarch / King Fleshpound / Abomination / Matriarch)

During wave time specimens spawn randomly at pre-determined locations near to the players, providing there is something obscuring the view between all players and the spawn.

Lesser ZEDs

Classified as lesser ZEDs, the Clot variants, Stalkers, Gorefasts and Crawlers are the most common enemies encountered. They mainly serve as both the main strike force and as cannon fodder, while more powerful ZEDs trail behind or among them towards the survivors. The health of these ZEDs does not scale with the game difficulty and player count; however, on harder difficulties, they are likely to sprint more frequently and will execute more powerful attacks and moves.

Players should never underestimate any of these types of ZEDs. While they are weak on their own, they are never so; all of them swarm in large groups that can overwhelm unaware or unprepared players, resulting in a quick death, especially if backed by more powerful ZEDs.

All lesser ZEDs, except for Gorefasts, are able to spawn from manholes in the ground or vents on ceilings and walls.

Medium ZEDs

Classified as medium ZEDs, the Bloat, Siren, Husk, and E.D.A.R are specialized ZEDs that can easily disrupt a group's efforts to survive. These ZEDs are decently tough, and possess special abilities that can cripple or outright deny certain strategies. The health and variety of attacks of these ZEDs will go up as difficulty and player count increases. Many of these ZEDs require their own approach to dispatch, as certain perks and weapons will vary on how to deal with them.

Large ZEDs

Classified as large ZEDs, the Quarter-Pound, Scrake and Fleshpound are the tanks and rending force of the specimen horde. Not only do they have a massive health pool, but they also have extremely powerful attacks and are resistant to most incapacitation techniques, such as fire panic, poison, and stuns. Targeting big ZEDs should always be prioritized by survivors, but intimate knowledge of how they operate, what their weaknesses are, and coordination are essential to defeat them.

Elite Variants

On higher difficulties, Elites, also sometimes referred to as King ZEDs, will spawn in place of their base specimen. There are 3 elite ZEDs that can spawn:

Rioters, armored albino Alpha Clots, will "rally" nearby ZEDs, enraging them and increasing their damage.
Elite Crawlers, albino Crawlers, explode into vision-obscuring and damaging gas when killed by means other than a headshot.
Gorefiends, dual-bladed and black-skinned Gorefasts, are capable of dealing massive amounts of damage and can tank much more damage.

Bosses

With the exception of certain Weekly Outbreaks and Versus Mode, at the last wave of each game, and for every 5th wave in Endless Mode, players have to face one of the game's bosses as a final challenge. Each boss has their own way of maintaining their health, their own "stages" to reach when they lose a certain amount of health, can spawn minions to support them, and has differing weaknesses.

Hans Volter, an old man wearing a life-support suit that augments his abilities, is equipped with 2 Mkb.42(H) Carbine Rifles, various grenades, and can drain the life of players.
The Patriarch, a heavily mutated Kevin Clamley, is equipped with a chaingun-rocket launcher arm and 3 health-regenerating syringers, and is supported by his "children".
King Fleshpound, an even bigger Fleshpound, can fire a laser beam out of its chest and is supported by Quarter-Pounds.
The Abomination, an armored Bloat, wields 2 giant axes and is capable of spawning its own unique minions by consuming any other ZED in its path.
The Matriarch, a mutated and augmented Rachel Clamley, wears a robotic battlesuit equipped with an arm cannon and a field emitter and is supported by E.D.A.R.s.

Versus ZEDs

In Killing Floor 2's Versus Mode players posses unique variants of regular ZEDs. While controlling them players are free to execute all the moves and attacks their regular counterparts have as well as some gamemode-specific attacks. Two of the basic stats of these ZEDs - health and damage are the subject of change via the Game Conductor mechanic.