Games like Doomsday Hero
Games like Doomsday Hero include Deadlight, PUBG: BATTLEGROUNDS, Broforce, Left 4 Dead 2, and Zombotron. We matched them by the tags players give Doomsday Hero on Steam (Action, Shooter, 2D, Platformer, and Zombies): closest matches first, and among equally close ones the better-known games.

Deadlight
Shared: Action · Platformer · Zombies

PUBG: BATTLEGROUNDS
Shared: Shooter · Survival · Action

Broforce
Shared: Action · 2D · Platformer

Left 4 Dead 2
Shared: Zombies · Shooter · Action

Zombotron
Shared: Action · 2D · Shooter

The Final Station
Shared: 2D · Action · Survival

Guns, Gore and Cannoli 2
Shared: Action · 2D · Side Scroller

My Friend Pedro
Shared: Action · Shooter · Indie

DayZ
Shared: Zombies · Survival · Shooter

Call of Duty®: Black Ops III
Shared: Shooter · Action · Zombies

Guns, Gore & Cannoli
Shared: Action · 2D · Side Scroller

Deadly 30
Shared: Action · Zombies · 2D

Resident Evil 4 (2005)
Shared: Action · Zombies · Adventure

Resident Evil 6
Shared: Action · Zombies · Third-Person Shooter

The Last of Us™ Part I
Shared: Zombies · Shooter · Post-apocalyptic

Skul: The Hero Slayer
Shared: Action · 2D · Platformer

Shank 2
Shared: Action · 2D · Side Scroller

Escape From Duckov
Shared: Action · Shooter · Adventure

Terraria
Shared: 2D · Survival · Adventure

Left 4 Dead
Shared: Action · Zombies · Shooter

Days Gone
Shared: Zombies · Action · Survival

Resident Evil 4
Shared: Action · Zombies · Third-Person Shooter

The Last Stand Legacy Collection
Shared: Action · Zombies · Survival

Remnant: From the Ashes
Shared: Action · Shooter · Adventure