Devastators are super attacks that the Prototypes can initiate. It causes a massive area damage to their surroundings at the cost of using up a portion of their critical mass health to execute. These moves can also be used while in Disguise.

Types

Tendril Barrage Devastator

The Tendril Barrage causes barbs made of hardened tendons to erupt from Alex's body in every direction, impaling everything around them for a fair distance. It will wipe out entire crowds of civilians and can cause extreme damage to Hunters and Super Soldiers. Even the larger Leader Hunters will take a fair amount of damage.

Armored vehicles like Tanks are highly resistant to its damage, but APCs are the only armored vehicles that are strangely vulnerable to it, depending on how far away they are from Alex, unless the player target lock-ons them from a long distance.

The Supreme Hunter also has this ability, but his version is slower than Alex's considering Alex can dodge his tendrils easily by running, jumping and air dashing around the Supreme Hunter even if Alex's movements are not fully upgraded.

The ground version has a certain quirk of causing additional "vacuum" damage, that is nearby objects and enemies sustain another round of damage when the tendrils retract. This is absent in the air version though the screen shake effect is present (that is absent in ground version).

Targeting an enemy before launching the attack will result in one of the tendrils visibly extending for an extremely long distance to hit it. This can be used to effectively snipe attack helicopters from far away.

Groundspike Graveyard Devastator

The Groundspike Graveyard is similar to the Groundspike power granted by the Claws. When used, it causes massive spikes of biomass to erupt from the ground, creating a deadly circle of spikes in close proximity to Alex. It is highly effective against hardened targets like Armor and buildings, but less effective than the Tendril Barrage against larger organic enemies due to its shorter range and smaller amount of spikes.

This Devastator can usually destroy a Military Base or Hive in a few hits and a few more in later stages of the game depending on difficulty. The air version gives the benefit of charging the attack while on the move in the air.

This is also the only Devastator that is very effective against Elizabeth Greene in On Instinct even on Hard Mode. However, the amount of damage from them against Greene is random depending where Alex is positioned at, sometimes they will do extreme damage on her tentacles, sometimes they will do only little to each of them or just one. And if Alex is way too close to her, then the Devastator will do very little or not do any damage to her due the spikes being a little far from Alex.

Critical Pain Devastator

Critical Pain fires a mass of hardened tendons from Alex's hands to crush a single target. It is the single most damaging move in the entire game, but can only be used to hit a single target. Anything that happens to be between Alex and the target will also be affected by the area air pressure caused from it. This devastator is similar to Tendril Black Hole ability from Prototype 2 except without tendrils sprouting from a target and pulled nearby objects in.

Its power is such that, short of bosses and buildings, there is nothing that will survive this attack unless playing on Normal or Hard Mode where some enemies will survive it, but will still get the job done due to its damage and if the player is very experienced with consuming small NPCs fast. The air version suspends Alex in the air at any level while executing the Devastator.

Pack Leader

The Pack Leader allows James Heller to call for a pack of Brawler Hunters to aid him in combat, initially only two. As Heller upgrades his mass, he can call for more of these, up to four Brawlers at one time. Heller can command these Brawlers to attack any specific target, much like giving orders to an attack dog.

When either Heller dismisses the pack or one of each is killed, they explode in a barrage of tendrils, causing additional damage to enemies and surroundings.

Heller acquires this ability after defeating and consuming Dr. Archer.

Biomass Expulsion Devastator

This Devastator in Prototype 2 for James Heller is a composition of a couple of moves and abilities from Prototype. This devastator is very similar to the Tendril Barrage Devastator from Prototype.

Upon activation on the ground, James Heller slams the floor, reminiscent of the Groundshatter move from the first game that launches nearby enemies upward, and then acts like a fragmentation grenade: he "explodes", releasing all biomass he had gained in a similar fashion to the Tendril Barrage Devastator in the previous title. If there is no Critical Mass upgrade present, the Biomass Expulsion kills any human-type enemy around Heller and deals heavy damage to more powerful creatures and vehicles. If the critical mass bar is fully charged, Biomass Expulsion becomes powerful enough to instantly leave hardy biological targets in the consuming range, if not killing them outright.

The ground shattering move is absent in the air variant of the devastator, for obvious reasons, though the execution resembles that of the first game's Air Knuckle Shockwave combined with the Tendril Barrage Devastator. It is highly effective against helicopters, because one fully charged Biomass Expulsion can destroy an entire strike team.

It should be noted that "Biomass Expulsion" is not an official name of this devastator, as it is simply called "Devastator" in-game. The name comes from "Biomass Expulsion Technology", mentioned by Dr. Koenig when Heller tells the doctor that he "exploded".

Heller acquires the devastator after defeating and consuming the Phase Two super soldier of Project Orion.

Juggernaut Pack

In the mission "A Labor of Love", James Heller makes futile attempts to break open reinforced doors to the Gentek Headquarters with his Hammerfists until he encounters an Alpha Juggernaut. Heller then dismembers it with his Blade and consumes it with his Hammerfists to obtain a special Juggernaut Pack ability and uses that to break down the doors. Subsequently, James Heller must consume an Alpha Juggernaut every time he wants to summon a Juggernaut Pack to replace killed ones. This ability is only available for this particular mission. When this ability is active, Heller gains power to destroy any vehicle and kill any enemy with a single hit.

Flyer Pack

Seen especially in the final battle between Mercer and Heller as well as some few battles with Evolved (especially Lawrence Foster and Lindsay Benhurst). After Alex Mercer started to use the Hammerfists, he can summon a horde of Flyers to attack Heller in a similar manner of the "Pack Leader" abilities displayed by Heller and Dr. Archer.

Trivia

• At the end of Memory in Death where we see Alex Mercer consuming a BlackWatch commander. There are two Tanks he is near to that are destroyed instantly by the Tendril Barrage. This is strange considering the Tanks throughout the game's story and free roam are highly resistant to the Tendril Barrage.
• After consuming Alex Mercer at the end of Prototype 2, Heller uses an attack similar to Tendril Barrage Devastator, but on much greater scale, destroying and consuming the majority of infected in the Red Zone.
• When James Heller executes his Biomass Expulsion, there are scab-like projectiles that are sent out in force. They may be hardened, which explains how they do so much damage. 
• If Heller needs to clear out a base or he needs a legitimate distraction, one can use the devastator while descending into the ocean. This causes the pack to almost instantly spawn and no form of detection of Heller to occur. The best thing is that it can all be done undercover. Just walk around the area where the distraction is needed and let the Pack do the rest.
• The slow motion effects of the Tendril Barrage and Groundspike Graveyard Devastators in Prototype can be skipped by pausing the game and then exiting the pause menu. (The same can be said with Bulletdive Drop and some missions that have slow motion)
• There is a strange powerful glitch of the ground version of Tendril Barrage in Prototype where if the player holds the power wheel section of Alex's powers when the tendrils retract, it will cause the tendrils to do significant damage on infected enemies including bosses.
• In the PS4 and Xbox One versions of Prototype known as the "Biohazard Bundle" edition. The colors of Tendril Barrage and Critical Pain have slightly changed from having a mixture of black and red to complete black.
• In Prototype 2, there is a cut version of a devastator attack, which is effectively the same as Alex Mercer's Tendril Barrage Devastator from Prototype. Whether or not this devastator attack is intended for use by Alex Mercer in a final boss fight is unknown.

Sources

• Prototype
• Prototype 2