Offensive Powers are abilities mutated due to the Blacklight infection present within Alex Mercer and James Heller. Each ability has its own purpose and can be adapted to a particular situation. However, Heller's abilities vary from those of Mercer.
- Main article: Blade
The Blade is a powerful and deadly cutting and thrusting weapon, perfect for slicing and swiping through even the toughest armored vehicles or infected hives. This attack power allows access to the second most powerful strikes available.
- Main article: Claws
Claws are the most prominent anti-personnel ability. Biomass is shifted into 4-digited, talon-like appendages that can be used to shred flesh and bone, cutting both the infected and military in half with a single sweep in some cases.
- Main article: Hammerfists
Hammerfists are primarily an anti-vehicle power. By shifting large amounts of biomass towards the hands, large hammer-like weapons are formed that are excellent for crushing both vehicles and infantry.
Unfortunately, Hammerfists are slow and inaccurate but allow the player to deal the greatest damage in the whole/all of the games available to the player, in the universe of Prototype and Prototype 2.
- Main article: Musclemass
Musclemass acts as a strength augmentation to Alex Mercer's arms. It greatly increases close combat damage and the distance debris can be thrown to deal with distant enemies.
- Main article: Whipfist
- Main article: Tendrils
The Tendrils power is an ability evolved by James Heller that allowed him to grapple enemies with the viral biomass. Upgraded, this ability acts as a devastator.
- Main article: Devastators
- In Prototype 2, the Musclemass ability has been replaced with Tendrils ability.
- James Heller's Blade arm and Claws resemble a military combat knife. Coincidentally, James himself was an ex-soldier.
- Heller also has the ability to perform a devastator attack with his Hammerfists, known as the "Hammerfist Dive Bomber Shockwave".
- Although not in the first game, Mercer has displayed his ability to use Tendrils, as shown in a cutscene in the mission Fall from Grace.