Games like Idle Survivor
Games like Idle Survivor include Vampire Survivors, Megabonk, Death Must Die, Halls of Torment, and Soulstone Survivors. We matched them by the tags players give Idle Survivor on Steam (Action Roguelike, Action, Casual, Bullet Hell, and Bullet Heaven): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Action Roguelike · Bullet Hell · Roguelite

Megabonk
Shared: Action Roguelike · Bullet Heaven · Bullet Hell

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

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

Soulstone Survivors
Shared: Action Roguelike · Bullet Heaven · Bullet Hell

Brotato
Shared: Action Roguelike · Bullet Hell · Bullet Heaven

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

Astro Prospector
Shared: Casual · Action Roguelike · Incremental

Boneraiser Minions
Shared: Action Roguelike · Bullet Hell · Roguelite

Hades
Shared: Action Roguelike · Action · Roguelite

Nordic Ashes: Survivors of Ragnarok
Shared: Action Roguelike · Bullet Heaven · Bullet Hell

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

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

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

Nova Drift
Shared: Bullet Hell · Action Roguelike · Roguelite

Hades II
Shared: Action · Action Roguelike · Roguelite

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

Yet Another Zombie Survivors
Shared: Action Roguelike · Bullet Heaven · Roguelite

Be My Horde
Shared: Action Roguelike · Bullet Hell · Bullet Heaven

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

Magicraft
Shared: Action Roguelike · Bullet Hell · Roguelite

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

Spirit Hunters: Infinite Horde
Shared: Action Roguelike · Action · Bullet Heaven

Rogue Legacy
Shared: Action Roguelike · Action · Roguelike