Games like Duck Paradox
Games like Duck Paradox include Vampire Survivors, Enter the Gungeon, Skul: The Hero Slayer, BALL x PIT, and Dead Cells. We matched them by the tags players give Duck Paradox on Steam (Singleplayer, Shoot 'Em Up, Arcade, Action Roguelike, and Bullet Hell): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Action Roguelike · Bullet Hell · Singleplayer

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

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

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

Dead Cells
Shared: Action Roguelike · Adventure · Singleplayer

Hollow Knight
Shared: Platformer · Singleplayer · Difficult

Spelunky
Shared: Action Roguelike · Platformer · Difficult

The Binding of Isaac: Rebirth
Shared: Action Roguelike · Singleplayer · Difficult

Megabonk
Shared: Action Roguelike · Bullet Hell · Singleplayer

20 Minutes Till Dawn
Shared: Action Roguelike · Shoot 'Em Up · Bullet Hell

Downwell
Shared: Action Roguelike · Arcade · Platformer

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

Hollow Knight: Silksong
Shared: Singleplayer · Difficult · Platformer

Rogue Legacy 2
Shared: Arcade · Platformer · Singleplayer

Risk of Rain (2013)
Shared: Action Roguelike · Platformer · Difficult

Rogue Legacy
Shared: Singleplayer · Platformer · Action Roguelike

Brotato
Shared: Singleplayer · Action Roguelike · Bullet Hell

Nuclear Throne
Shared: Action Roguelike · Bullet Hell · Difficult

Exit the Gungeon
Shared: Arcade · Singleplayer · Bullet Hell

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

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

Celeste
Shared: Difficult · Singleplayer · Platformer

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

Dungreed
Shared: Action Roguelike · Singleplayer · Pixel Graphics