Sabotage is a skill that is unlockable by an Engineer, Infiltrator, or Sentinel Shepard as well as Garrus, Tali, and Kaiden. It can be unlocked in the skill tree as Decryption.
You NEED a target to unlock this achievement. During combat you can cast Sabotage against an enemy and then wait until it recharges.
Alternatively a quicker way to do this is to cast Sabotage on the Citadel Rapid Transport terminals. Once you reach the Citadel you'll find orange terminals that let you fast travel around the Citadel but they also count as targets for Sabotage. Simply save in front of one cast Sabotage and then reload your save to cut down on the time it takes for your ability to recharge.
When your team mates cast Sabotage it counts toward the 25.