Games like Slaughter 3: The Rebels
Games like Slaughter 3: The Rebels include Gears 5, My Friend Pedro, Serious Sam 4, Hotline Miami, and DOOM Eternal. We matched them by the tags players give Slaughter 3: The Rebels on Steam (Action, Indie, Adventure, Gore, and Violent): closest matches first, and among equally close ones the better-known games.

Gears 5
Shared: Action · Adventure · Third-Person Shooter

My Friend Pedro
Shared: Action · Indie · Gore

Serious Sam 4
Shared: Action · Gore · Shooter

Hotline Miami
Shared: Action · Indie · Violent

DOOM Eternal
Shared: Action · Gore · Violent

171
Shared: Action · Indie · Gore

Just Cause 4 Reloaded
Shared: Action · Adventure · Third-Person Shooter

CARRION
Shared: Gore · Action · Indie

HELLDIVERS™ 2
Shared: Action · Third-Person Shooter · Shooter

OUTRIDERS
Shared: Action · Adventure · Third-Person Shooter

Grand Theft Auto V Legacy
Shared: Action · Adventure · Shooter

Bulletstorm: Full Clip Edition
Shared: Action · Gore · Adventure

Hotline Miami 2: Wrong Number
Shared: Gore · Action · Violent

Escape From Duckov
Shared: Action · Adventure · Shooter

Warhammer 40,000: Space Marine - Anniversary Edition
Shared: Action · Third-Person Shooter · Gore

Red Dead Redemption 2
Shared: Action · Adventure · Shooter

Necromunda: Hired Gun
Shared: Action · Adventure · Gore

Prodeus
Shared: Action · Gore · Indie

PUBG: BATTLEGROUNDS
Shared: Shooter · Action · Third-Person Shooter

Daymare: 1998
Shared: Action · Adventure · Indie

Bright Memory: Infinite
Shared: Action · Indie · Shooter

The Walking Dead: Saints & Sinners
Shared: Action · Gore · Adventure

12 is Better Than 6
Shared: Action · Indie · Shooter

Aimlabs
Shared: Action · Shooter · Third-Person Shooter