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

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

Megabonk
Shared: Roguelike · Action Roguelike · Bullet Heaven

Vampire Survivors
Shared: Action Roguelike · Bullet Hell · Pixel Graphics

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

BALL x PIT
Shared: Action · Roguelike · Bullet Hell

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

Soulstone Survivors
Shared: Action Roguelike · Bullet Heaven · Roguelike

Brotato
Shared: Roguelike · Action Roguelike · Bullet Hell

The Binding of Isaac: Rebirth
Shared: Roguelike · Action Roguelike · Pixel Graphics

Noobs Want to Live
Shared: Roguelike · Action · Bullet Hell

Nuclear Throne
Shared: Roguelike · Action Roguelike · Action

Atomicrops
Shared: Action · Roguelike · Bullet Hell

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

20 Minutes Till Dawn
Shared: Action Roguelike · Bullet Hell · Pixel Graphics

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

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

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

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

Scarlet Tower
Shared: Action Roguelike · Bullet Heaven · Pixel Graphics

Dead Cells
Shared: Roguelike · Action Roguelike · Pixel Graphics

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

Boneraiser Minions
Shared: Action Roguelike · Bullet Hell · Pixel Graphics

Sephiria
Shared: Action Roguelike · Roguelike · Action

Realm of the Mad God Exalt
Shared: Roguelike · Pixel Graphics · Bullet Hell