Games like Serious Sam: Tormental
Games like Serious Sam: Tormental include Vampire Survivors, Enter the Gungeon, Nuclear Throne, SYNTHETIK: Legion Rising, and Megabonk. We matched them by the tags players give Serious Sam: Tormental on Steam (Action, Action Roguelike, Indie, Bullet Hell, and Roguelite): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Action Roguelike · Bullet Hell · Roguelite

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

Nuclear Throne
Shared: Action Roguelike · Indie · Action

SYNTHETIK: Legion Rising
Shared: Action · Indie · Action Roguelike

Megabonk
Shared: Action Roguelike · Indie · Roguelite

Hades
Shared: Action Roguelike · Indie · Roguelite

Brotato
Shared: Action Roguelike · Bullet Hell · Roguelike

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

BALL x PIT
Shared: Action · Roguelite · Bullet Hell

Voidigo
Shared: Action Roguelike · Bullet Hell · Twin Stick Shooter

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

Relic Hunters Zero: Remix
Shared: Action · Action Roguelike · Twin Stick Shooter

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

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

Gunfire Reborn
Shared: Roguelite · Action · Indie

Blazing Beaks
Shared: Action Roguelike · Action · Roguelite

Streets of Rogue
Shared: Action Roguelike · Roguelite · Action

Atomicrops
Shared: Action · Bullet Hell · Action Roguelike

Hades II
Shared: Action · Roguelite · Action Roguelike

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

Risk of Rain (2013)
Shared: Action Roguelike · Indie · Action

Ravenswatch
Shared: Action Roguelike · Action · Co-op

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

Soulstone Survivors
Shared: Action Roguelike · Bullet Hell · Roguelite