Games like The KillBox: Aquarius
Games like The KillBox: Aquarius include DOOM Eternal, DOOM, GoreBox, Wolfenstein II: The New Colossus, and Trepang2. We matched them by the tags players give The KillBox: Aquarius on Steam (Gore, Violent, FPS, and Shooter): closest matches first, and among equally close ones the better-known games.

DOOM Eternal
Shared: Gore · FPS · Violent

DOOM
Shared: Gore · FPS · Shooter

GoreBox
Shared: Gore · Violent · FPS

Wolfenstein II: The New Colossus
Shared: Gore · FPS · Violent

Trepang2
Shared: Shooter · FPS · Gore

Serious Sam 4
Shared: Gore · FPS · Shooter

Call of Duty®
Shared: FPS · Shooter · Violent

Insurgency: Sandstorm
Shared: FPS · Shooter · Gore

Call of Duty®: Warzone™
Shared: FPS · Shooter · Violent

Bulletstorm: Full Clip Edition
Shared: Gore · FPS · Violent

Back 4 Blood
Shared: Gore · FPS · Shooter

Left 4 Dead 2
Shared: FPS · Shooter · Gore

Ready or Not
Shared: FPS · Shooter · Violent

Warhammer 40,000: Darktide
Shared: FPS · Gore · Violent

The Darkness II
Shared: Gore · FPS · Shooter

Pavlov
Shared: Shooter · FPS · Gore

RoboCop: Rogue City
Shared: FPS · Gore · Shooter

Maximum Action
Shared: Gore · FPS · Violent

Killing Floor
Shared: FPS · Violent · Gore

Killing Floor 2
Shared: Gore · FPS · Shooter

Blood Trail
Shared: Gore · Violent · Shooter

ULTRAKILL
Shared: Gore · FPS · Shooter

POSTAL 2
Shared: Violent · Gore · FPS

Serious Sam Fusion 2017 (beta)
Shared: Gore · FPS · Violent