Games like Mutant Survivors
Games like Mutant Survivors include Vampire Survivors, Megabonk, Brotato, Deep Rock Galactic: Survivor, and Halls of Torment. We matched them by the tags players give Mutant Survivors on Steam (Action Roguelike, Bullet Hell, Roguelite, Survival, and Arcade): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Action Roguelike · Bullet Hell · Roguelite

Megabonk
Shared: Action Roguelike · Roguelite · Bullet Hell

Brotato
Shared: Bullet Hell · Action Roguelike · Singleplayer

Deep Rock Galactic: Survivor
Shared: Action Roguelike · Roguelite · Bullet Hell

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

BALL x PIT
Shared: Roguelite · Bullet Hell · Action Roguelike

20 Minutes Till Dawn
Shared: Action Roguelike · Bullet Hell · Roguelite

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

Hades
Shared: Action Roguelike · Roguelite · Action

Soulstone Survivors
Shared: Action Roguelike · Roguelite · Bullet Hell

Rogue: Genesia
Shared: Bullet Hell · Action Roguelike · Roguelite

Nova Drift
Shared: Bullet Hell · Roguelite · Action Roguelike

God Of Weapons
Shared: Action Roguelike · Roguelite · Bullet Hell

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

Magicraft
Shared: Action Roguelike · Bullet Hell · Roguelite

Tower of Babel: Survivors of Chaos
Shared: Action Roguelike · Bullet Hell · Roguelite

Boneraiser Minions
Shared: Action Roguelike · Bullet Hell · Roguelite

Windowkill
Shared: Action Roguelike · Bullet Hell · Action

Yet Another Zombie Survivors
Shared: Action Roguelike · Roguelite · Arcade

FatalZone
Shared: Action Roguelike · Bullet Hell · Survival

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

Nuclear Throne
Shared: Action Roguelike · Bullet Hell · Roguelite

Glyphica: Typing Survival
Shared: Action Roguelike · Bullet Hell · Roguelite

UnderMine
Shared: Action Roguelike · Roguelite · Action