Complete an Operative Primary Objective within 5 seconds of breaking disguise
Required Class: Operative
Required Ability: Standard Operative Kit
Ability Unlocked: Rank 1 (automatic from start)
To go into disguise, go to any dead enemy's body and hold . The only objective for an operative is to hack. Oddly, hacking breaks disguise and is usually fairly slow. Also, if you die, the other team will likely take off your hack box and cause you to do it all over again. The scenario the game wants was as follows: You died at 95% or so hacking. You spawn, get in disguise, and go back to the objective. You then finish the hacking. This is extremely rare and unlikely, especially against bots. So what you need to do is hack until 95%, disguise yourself with a body nearby (or create one), then finish the hack. Remember the disguise breaks when you start hacking.
Note: As long as you are in disguise when an operative objective is complete (by someone else) you will still get the achievement. You had to have been a part of the hack at some point.