Malva sector on Venus is a
Dark Sector Excavation
, level 10-20 and how I got this achievement. Unfortunately, with the starchart change, it is no longer an excavation but a survival. If it's the same map though, that should work well if you can go into a stealth mode. A potential substitute according to Geoffistopheles is Venus - Kiliken with level 5-7 Corpus, although not as good as infested.
I used Loki for the invisibility, and this map because one of the Corpus tilesets spawns you right next to several zip lines on a roof. That is one of the only tilesets in any mission that has native zip lines and is fairly easy to access.
The tileset spawn you want spawns you on a roof near some ziplines. If you don't get the roof spawn, abort the mission, and start it again. I got it 1st try, then 4th try doing this.
From there, just jump down off the roof, activate the Extractor, wait for it to die to the infested, then run through or around the building back to the ziplines. If you stand under them and press
it will automatically put you onto the lower one if you're standing close enough!
So, get the Infested to follow you there, activate Invisibility, jump onto the zipline and kill the Infested with a silent weapon(I used Loki's mod Hushed Invisibility which makes weapons silent while invisible). Otherwise a bow would work well if it's strong enough.
The Infested will keep spawning, just lead them to the zip line if they aren't close enough, and it goes fast! I got all 30 in a couple minutes.
Note: I have Ivara, but she's at level 1, so I couldn't test out her ziplines. If you don't have Ivara, Loki works really well on this map! If you don't have Ivara OR Loki, Loki's invisibility unlocks sooner than Ivara's Prowl by a few levels.
My Loki Prime max speed build(Sprint speed 1.96):
My Loki Prime invisibility build(203% Power Duration):