Tactical Specialist is an achievement in Call of Duty: Black Ops III. It requires the player to obtain five medals based on a Specialist Ability in a single game.
For this achievement/trophy, it's preferable to equip the Tier 1 perk Overclock, as this will decrease the charging time of a Specialist ability by 25%. Close-quarters maps like Nuk3town or Combine can help with racking up kills to speed up the charging time. The achievement doesn't ask for a specific ability, but it's easier to use disorienting abilities such as Psychosis or Kinetic Armor. Getting five kills with the ability active unlocks the achievement.