The Outer Worlds

For anyone who wants to make it quick. Find a group of infected soldiers (garden region) make a save file before killing them , kill them , make a NEW file , reload a previous save, kill them again.

The achievement unlocks when you kill any combination of 50 enemies that can be characterized as parasite spawnlings or hosts. These are enemies unique to Eridanos. They respawn so there is no shortage of targets. Even after you complete the Murder on Eridanos for The Outer Worlds DLC in a manner that resolves the parasite threat, you will continue to encounter hosts and parasites so the achievement is unmissable and will come readily during normal gameplay.

The game’s system save file maintains a count of kills that count towards the achievement. Thus, it is easy to grind this achievement if you want to force it to pop early. If you make a save before killing host(s) &/or spawnling(s), save again in a separate slot to update the system save file, you can then load the first save and kill the same enemy or enemies again to increase your kill count.

Doing this repeatedly will pop the achievement on your 50th kill. If you choose to use this method, for convenience, turn on the console’s achievement tracker. Designate this achievement as a favorite so you can monitor your progress.

Nice-to-know background info not essential to unlocking the achievement: Parasite spawnlings resemble mantipillars and, like them, are able to burrow into the ground and reemerge, unexpectedly, at a different location. They are, however, a different creature that has a parasitic life cycle. The following is a summary of the lore regarding the parasites acquired through diligent exploration of Eridanos and completing all side quests.

• A queen lays eggs that hatch to produce worms or slugs. These attach themselves to people and enmesh themselves into the humans’ nervous systems stimulating their pleasure centers. Because they induce a state of euphoria, the Eridanos Administrator used them in his Morale Improvement Program. With a single parasite, the humans are happy & friendly, exhibiting no signs of hostility and are highly productive Rizzo employees.
• Nevertheless, as with most poorly understood corporate projects in Halcyon, the Morale Improvement Program spiraled out of control. The worms multiplied with numerous parasites infecting the same host. Humans with multiple parasites are no longer sane but homicidal maniacs. They are no longer human but humanoid enemies who exhibit extreme hostility towards all non-infected. In addition to weaponless melee attacks, they vomit highly toxic parasitic matter.