Games like Instability
Games like Instability include Thronefall, Stronghold: Definitive Edition, Border Pioneer, Total War: WARHAMMER III, and Creeper World 4. We matched them by the tags players give Instability on Steam (Action, Strategy, Tower Defense, RTS, and Bullet Hell): closest matches first, and among equally close ones the better-known games.

Thronefall
Shared: Strategy · Tower Defense · Action

Stronghold: Definitive Edition
Shared: Strategy · City Builder · RTS

Border Pioneer
Shared: Strategy · Tower Defense · Action

Total War: WARHAMMER III
Shared: Strategy · RTS · Action

Creeper World 4
Shared: Tower Defense · RTS · Strategy

Bad North: Jotunn Edition
Shared: Tower Defense · Real Time Tactics · Wargame

Men of War: Assault Squad 2
Shared: Strategy · Action · RTS

Stronghold Crusader: Definitive Edition
Shared: Strategy · City Builder · Real Time Tactics

GemCraft - Frostborn Wrath
Shared: Tower Defense · Strategy · RTS

Ultimate Epic Battle Simulator 2
Shared: Strategy · Action · RTS

Aliens: Dark Descent
Shared: Strategy · Action · RTS

WARNO
Shared: Strategy · RTS · Real Time Tactics

Kingdom Rush - Tower Defense
Shared: Strategy · Tower Defense · Action

Your Only Move Is HUSTLE
Shared: Action · Strategy · 2D

Infested Planet
Shared: Strategy · Action · Tower Defense

Kingdom Rush Vengeance - Tower Defense
Shared: Strategy · Tower Defense · 2D

Kingdom Rush 6: Genesis TD
Shared: Strategy · Action · Tower Defense

Total War: WARHAMMER II
Shared: Strategy · RTS · Action

Stronghold HD (2012)
Shared: City Builder · Real Time Tactics · Tower Defense

Wargame: Red Dragon
Shared: Strategy · RTS · Wargame

Bee Island
Shared: Strategy · Tower Defense · City Builder

Total War: ROME REMASTERED
Shared: Strategy · Action · RTS

Creeper World IXE
Shared: Tower Defense · RTS · Real Time Tactics

Door Kickers
Shared: Strategy · Action · 2D