Games like Undercroft Warriors
Games like Undercroft Warriors include Bit Blaster XL, Chippy, BALL x PIT, Sky Force Reloaded, and Enter the Gungeon. We matched them by the tags players give Undercroft Warriors on Steam (Shoot 'Em Up, Top-Down Shooter, Twin Stick Shooter, Bullet Hell, and Difficult): closest matches first, and among equally close ones the better-known games.

Bit Blaster XL
Shared: Shoot 'Em Up · Bullet Hell · Difficult

Chippy
Shared: Twin Stick Shooter · Shoot 'Em Up · Bullet Hell

BALL x PIT
Shared: Bullet Hell · Shoot 'Em Up · Arcade

Sky Force Reloaded
Shared: Shoot 'Em Up · Top-Down Shooter · Bullet Hell

Enter the Gungeon
Shared: Bullet Hell · Difficult · Twin Stick Shooter

Planes, Bullets and Vodka
Shared: Shoot 'Em Up · Bullet Hell · Shooter

Nex Machina
Shared: Twin Stick Shooter · Bullet Hell · Shoot 'Em Up

Assault Android Cactus+
Shared: Shoot 'Em Up · Twin Stick Shooter · Bullet Hell

Bot Vice
Shared: Top-Down Shooter · Shoot 'Em Up · Bullet Hell

LUFTRAUSERS
Shared: Bullet Hell · Shoot 'Em Up · Arcade

Nuclear Throne
Shared: Difficult · Bullet Hell · Top-Down Shooter

KILL KNIGHT
Shared: Top-Down Shooter · Bullet Hell · Difficult

Waves
Shared: Shoot 'Em Up · Bullet Hell · Twin Stick Shooter

Cyberhunt
Shared: Shoot 'Em Up · Twin Stick Shooter · Arcade

DoDonPachi Resurrection
Shared: Shoot 'Em Up · Top-Down Shooter · Bullet Hell

Vampire Survivors
Shared: Bullet Hell · 2D · Pixel Graphics

ZeroRanger
Shared: Shoot 'Em Up · Bullet Hell · Arcade

UBERMOSH Vol.5
Shared: Arcade · Bullet Hell · Top-Down Shooter

BLUE REVOLVER
Shared: Shoot 'Em Up · Bullet Hell · Arcade

Star of Providence
Shared: Shoot 'Em Up · Bullet Hell · Difficult

Nova Drift
Shared: Shoot 'Em Up · Bullet Hell · Arcade

Ikaruga
Shared: Shoot 'Em Up · Bullet Hell · Arcade

Voidigo
Shared: Twin Stick Shooter · Shoot 'Em Up · Bullet Hell

Sektori
Shared: Shoot 'Em Up · Twin Stick Shooter · Top-Down Shooter