Games like Unforgotten: Ordinance
Games like Unforgotten: Ordinance include Outlast, Layers of Fear (2016), Little Nightmares II, Five Nights at Freddy's: Security Breach, and SOMA. We matched them by the tags players give Unforgotten: Ordinance on Steam (Horror, Psychological Horror, Atmospheric, Multiple Endings, and Adventure): closest matches first, and among equally close ones the better-known games.

Outlast
Shared: Horror · Atmospheric · Psychological Horror

Layers of Fear (2016)
Shared: Horror · Psychological Horror · Atmospheric

Little Nightmares II
Shared: Horror · Adventure · Atmospheric

Five Nights at Freddy's: Security Breach
Shared: Horror · Singleplayer · Multiple Endings

SOMA
Shared: Horror · Psychological Horror · Atmospheric

No, I'm not a Human
Shared: Horror · Psychological Horror · Atmospheric

Escape the Backrooms
Shared: Horror · Psychological Horror · Adventure

MiSide
Shared: Psychological Horror · Horror · Atmospheric

Firewatch
Shared: Atmospheric · Adventure · Singleplayer

Poppy Playtime
Shared: Horror · Singleplayer · Psychological Horror

Little Nightmares
Shared: Horror · Atmospheric · Adventure

Darkwood
Shared: Horror · Psychological Horror · Adventure

SILENT HILL 2
Shared: Horror · Psychological Horror · Atmospheric

Visage
Shared: Horror · Psychological Horror · Atmospheric

What Remains of Edith Finch
Shared: Atmospheric · Adventure · Walking Simulator

The Beast Inside
Shared: Horror · Adventure · Psychological Horror

Still Wakes the Deep
Shared: Horror · Psychological Horror · Atmospheric

SILENT HILL: Townfall
Shared: Horror · Psychological Horror · Adventure

Amnesia: A Machine For Pigs
Shared: Horror · Atmospheric · Psychological Horror

Mouthwashing
Shared: Horror · Psychological Horror · Atmospheric

[Chillas Art] The Convenience Store
Shared: Horror · Psychological Horror · Adventure

Among the Sleep - Enhanced Edition
Shared: Horror · Atmospheric · Adventure

Scanner Sombre
Shared: Horror · Atmospheric · Psychological Horror

Outlast 2
Shared: Horror · Psychological Horror · Atmospheric