Games like Nine Nines
Games like Nine Nines include Broken Arrow, Age of Darkness: Final Stand, Company of Heroes 3, Thronefall, and Creeper World 4. We matched them by the tags players give Nine Nines on Steam (Action RTS, Wargame, Real Time Tactics, Tower Defense, and PvE): closest matches first, and among equally close ones the better-known games.

Broken Arrow
Shared: Wargame · Action RTS · Real Time Tactics

Age of Darkness: Final Stand
Shared: Action RTS · Tower Defense · PvE

Company of Heroes 3
Shared: Wargame · Action RTS · Strategy

Thronefall
Shared: Tower Defense · Action RTS · Strategy

Creeper World 4
Shared: Wargame · Real Time Tactics · Tower Defense

Ukrainian Warfare: Gostomel Heroes
Shared: Wargame · Real Time Tactics · PvE

Bloons TD 6
Shared: Tower Defense · Strategy · 3D

Last Train Home
Shared: Real Time Tactics · Strategy · Wargame

ZeroSpace
Shared: Action RTS · Wargame · Real Time Tactics

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

Bee Island
Shared: Tower Defense · Action RTS · Strategy

Rogue Tower
Shared: Tower Defense · Strategy · 3D

WARNO
Shared: Wargame · Real Time Tactics · Strategy

Tower Dominion
Shared: Tower Defense · Strategy · Base Building

Minimalist Tower Defense
Shared: Tower Defense · Real Time Tactics · Strategy

Artisan TD
Shared: Tower Defense · Difficult · Strategy

Kingdom Rush Frontiers - Tower Defense
Shared: Tower Defense · Strategy · Difficult

Element TD 2 - Tower Defense
Shared: Real Time Tactics · Tower Defense · PvE

Wargame: Red Dragon
Shared: Wargame · Strategy · Real Time Tactics

9-Bit Armies: A Bit Too Far
Shared: Action RTS · Wargame · Real Time Tactics

Sudden Strike 4
Shared: Real Time Tactics · Action RTS · Strategy

Warhammer Age of Sigmar: Realms of Ruin
Shared: Action RTS · Real Time Tactics · Strategy

Northend Tower Defense
Shared: Tower Defense · Action RTS · Real Time Tactics

Stronghold Crusader: Definitive Edition
Shared: Real Time Tactics · Strategy · Tower Defense