Load and Pop
You may need to kill around a few Heavily Armored Troops before it pops. Mission 7 has 5 of them and you can checkpoint after killing all 5, the game will keep your killed count.
If the Humanoid Gekko Achievement does not pop either, Try loading V7 and hitting continue. Once the level loads run to the far right side, A boxing Dwarf Gekko Should spawn. Kill it and it should pop the achievement.
Next load V7-2 For the final boss achievement.
Vicious Tiger deserves thanks for providing the last achievement. Amateur radio operator.
Last update I'm going to do, posted a save before I bought all the customization.