Halo Wars 2

This achievement may not come as naturally like the others in this DLC, however, it can still be obtained rather quickly through two or three matches of Solo Blitz Firefight.

To begin, head into Blitz Mode and craft a deck for Sergeant Johnson, making sure to include the Colossus card. The rest of the cards in this deck can vary to whatever suits your desire. Now start a Solo Firefight match, send your starting units to capture all three Control Points, and then recycle the cards in your hand until you draw a Colossus unit. If you have enough energy, summon the mech onto the battlefield; if not, hold out on the early waves with your starting units until you can gather enough energy required to call in the Colossus.

With the mech out on the playing field, you can now move it around the map, hunting and attacking enemies. When each new enemy wave starts, note which type of units spawn into the map; if its air units or vehicular units, have your Colossus hang back as to avoid losing health, but if its infantry units, move the mech to their location and tap to execute the "Stomp." This attack will force the mech into a slow animation where it stops firing its main cannons, instead gearing up to stomp on its targeted foes. The attack deals a lot of damage and has generous splash damage, so even enemies five feet away can/will die from the stomp.

You should be able to net anywhere from 15-20+ Stomp kills during a single match before things get a little too hectic on the later, more difficult rounds. Keep in mind that you can have multiple Colossi out on the map, thus allowing you to potentially cover more ground for kills during the infantry-heavy waves. Once you have killed fifty enemies with the mech's Stomp ability, this achievement will unlock.

NOTE: If you have a boosting partner, this achievement can be obtained much easier/quicker by going toe-to-toe in a 1v1 Skirmish match, where one player chooses a Banished leader and the other Sgt. Johnson. When the match begins, the Banished player should work on building as many Grunt units as possible and then sending them to the center of the map. Here, the Sgt. Johnson player can use the Colossus' Stomp ability on the four-to-five dozen Grunts, effectively speeding up the progress of the achievement as opposed to doing it alone in Firefight.