This trophy is a bit of a grind, but you will get this trophy well before you earn Over Engineered.
You need to complete 100 objective waves, and you will encounter 5 of them per game. All of the waves are timed, and failing any of them will end your game.
Waves 3, 6, and 9 are random challenges, such as “Kill all Special Zombies,” “Defend the Objective,” and “Escort the V.I.Z.” Each map has its own set of challenges, and the map specific trophies will have more detail on the ones you can expect to find.
Wave 10 is always a Boss. You just have to kill the boss within the time limit.
Wave 11 is an Escape. You have 1:05 to get to a specific zone and you must be in the zone when the time expires.
The trophy will pop as soon as your 100th objective wave is complete.