Games like Nightmare: The Lunatic
Games like Nightmare: The Lunatic include Dead Cells, The Binding of Isaac: Rebirth, Skul: The Hero Slayer, Hades, and Vampire Survivors. We matched them by the tags players give Nightmare: The Lunatic on Steam (Action Roguelike, Hack and Slash, Difficult, Replay Value, and Pixel Graphics): closest matches first, and among equally close ones the better-known games.

Dead Cells
Shared: Action Roguelike · Roguelike · Pixel Graphics

The Binding of Isaac: Rebirth
Shared: Action Roguelike · Replay Value · Difficult

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

Hades
Shared: Action Roguelike · Hack and Slash · Roguelite

Vampire Survivors
Shared: Action Roguelike · Pixel Graphics · Roguelite

The Binding of Isaac
Shared: Action Roguelike · Replay Value · Difficult

Rogue Legacy
Shared: Action Roguelike · Roguelike · Platformer

Hollow Knight
Shared: Difficult · Metroidvania · Souls-like

Risk of Rain (2013)
Shared: Action Roguelike · Roguelike · Pixel Graphics

Dungreed
Shared: Action Roguelike · Pixel Graphics · Roguelite

Hades II
Shared: Hack and Slash · Action Roguelike · Roguelite

BlazBlue Entropy Effect
Shared: Action Roguelike · Replay Value · Pixel Graphics

Astral Ascent
Shared: Action Roguelike · Hack and Slash · Roguelite

Spelunky
Shared: Action Roguelike · Difficult · Roguelike

Death Must Die
Shared: Action Roguelike · Pixel Graphics · Roguelite

Enter the Gungeon
Shared: Action Roguelike · Difficult · Pixel Graphics

Hollow Knight: Silksong
Shared: Difficult · Metroidvania · Souls-like

Moonlighter
Shared: Hack and Slash · Pixel Graphics · Action Roguelike

Nuclear Throne
Shared: Action Roguelike · Difficult · Pixel Graphics

Caveblazers
Shared: Action Roguelike · Pixel Graphics · Roguelite

Noita
Shared: Difficult · Pixel Graphics · Roguelike

Halls of Torment
Shared: Action Roguelike · Roguelite · Pixel Graphics

Blasphemous
Shared: Pixel Graphics · Souls-like · Metroidvania

Megabonk
Shared: Action Roguelike · Roguelite · Roguelike