PED Marine

PED Marines are Federation Marines of the Galactic Federation with a Phazon Enhancement Device attached to their suit. With the attachment of the PED, PED Marines can utilize Phazon to increase the power of their armor. While active, the PED enchances the attack and defense systems of their armorsuits, making the much stronger than normal marines.

While the power jump is indeed considerable, the increase is based on the original weaponry before activation. For example, a standard GF Trooper's pulse laser does poor damage even compared to Samus's Power Beam. When the P.E.D. is activated, the weapons strength does get a dramatic increase, but will be inferior to a comparatively enhanced Power Beam. With this in mind, it is still a very powerful weapon, bringing a standard trooper to the general threat level of Samus herself, in a sense.

Logbook
Metroid Prime 3: Corruption: "The Federation has created a system that utilizes Phazon to increase the power of the armor worn by GF Marines. While active, the Phazon unit enhances the attack and defense systems of the armorsuit."

Trivia

 * In Metroid Prime 3: Corruption, when Samus is traversing to a landing site, she sees a trio of Marines fighting a trio of Pirates. Two Marines die and then the third Marine activates his PED suit, fires three blasts, and kills the Pirates.
 * In a trailer for the game, a PED Marine is seen defeating a Berserker Lord with relative ease, showing the power they possess.