Games like Immunity Protocol
Games like Immunity Protocol include Vampire Survivors, BALL x PIT, Brotato, Megabonk, and Halls of Torment. We matched them by the tags players give Immunity Protocol on Steam (Action, Action Roguelike, Roguelike, Top-Down Shooter, and Arcade): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Action Roguelike · Bullet Hell · Roguelite

BALL x PIT
Shared: Action · Roguelike · Arcade

Brotato
Shared: Roguelike · Action Roguelike · Bullet Hell

Megabonk
Shared: Action Roguelike · Roguelike · Action

Halls of Torment
Shared: Action Roguelike · Roguelike · Bullet Hell

Skul: The Hero Slayer
Shared: Action · Action Roguelike · Roguelike

Deep Rock Galactic: Survivor
Shared: Action Roguelike · Top-Down Shooter · Bullet Hell

Hades
Shared: Action Roguelike · Action · Roguelite

Nuclear Throne
Shared: Action Roguelike · Roguelike · Action

Rogue Legacy
Shared: Roguelike · Action Roguelike · Action

Death Must Die
Shared: Action Roguelike · Bullet Hell · Action

The Binding of Isaac
Shared: Action Roguelike · Roguelike · Action

Soulstone Survivors
Shared: Action Roguelike · Roguelike · Bullet Hell

Tower of Babel: Survivors of Chaos
Shared: Action Roguelike · Roguelike · Action

Yet Another Zombie Survivors
Shared: Action Roguelike · Top-Down Shooter · Arcade

Nova Drift
Shared: Action Roguelike · Bullet Hell · Arcade

Enter the Gungeon
Shared: Action Roguelike · Roguelike · Bullet Hell

The Binding of Isaac: Rebirth
Shared: Action Roguelike · Roguelike · Indie

Hades II
Shared: Action · Roguelike · Action Roguelike

Dead Cells
Shared: Roguelike · Action Roguelike · Roguelite

20 Minutes Till Dawn
Shared: Action Roguelike · Bullet Hell · Top-Down Shooter

Tiny Rogues
Shared: Action Roguelike · Top-Down Shooter · Bullet Hell

Risk of Rain 2
Shared: Action Roguelike · Roguelike · Action

The Spell Brigade
Shared: Action Roguelike · Bullet Hell · Roguelike