Fastest Possible Way - Need 5 friends
Setup
Ranked Match
1 Round Match
Garden Map
Warmachine
All COG's run into the mist in the greenhouse and die
(this counts as one win for all Locust team members towards the total of 10)
Repeat ten times and achievement pops up
If all six of you need the achievement just alternate between all the COGS and all the Locusts running into the greenhouse mist each (one round) match
15 minutes max to achieve if not alternating
30 minutes max to achieve if you are alternating
Note: this also counts towards your total of hosting 50 ranked matches achievement if you are the host