Remnant II

Aberrations are the red ghost like enemies.
They are a more powerful versions of usual enemies and can be found almost everywhere but they don't spawn as normal foes. You can think at them as mini boss.

This is a list of some of them:

1. The Progeny - corrupted version of a Slug Parasite (can be found in The Hatchery, The Dark Conduit, The Putrid Domain)
2. E.D. Alpha (found at the main hall of the Tower of the Unseen) - this boss also spawns smaller enemies that count towards the achievement. (thanks Killbomb)
3. Fetid Corpse - corrupted version of N'Erud Zombie (can be found all around N'Erud)
4. W.D. 109 - corrupted version of Robot Grunt (can be found in Void Vessel Facility, The Putrid Domain, Vault of the Formless)
5. Abomination - corrupted version of the Corpse Ball (N'Erud)
6. Grime Crawler (Sewer event in Butcher's Quarter or Cotton's Kiln)
7. Firth: The Oathkeeper - aberration of a Ranged Fae (Card Jester event)
8. The Weald Stalker and The Gnarled Archer - version of the Root Sniper (Forgotten Field, The Expanding Glade and Imperial Gardens)

This is a solution for the aberrations achievements but it requires the awakened king dlc (both of these glitched on me in the base game) so if this isn't welcomed here because its base game just let me know and I'll remove it this solution works as of 17/11/2023 also if its patched I'll remove this solution its pretty simple I explain everything in the video