Games like HORDE
Games like HORDE include Vampire Survivors, Skul: The Hero Slayer, Rogue Legacy, Windowkill, and Hades. We matched them by the tags players give HORDE on Steam (Action, Arcade, Action Roguelike, 2D, and Sci-fi): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Action Roguelike · 2D · Indie

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

Rogue Legacy
Shared: Action · Action Roguelike · Indie

Windowkill
Shared: Action · Action Roguelike · Arcade

Hades
Shared: Action Roguelike · Action · Indie

Risk of Rain Returns
Shared: Action Roguelike · 2D · Action

BALL x PIT
Shared: Action · Arcade · Action Roguelike

Megabonk
Shared: Action Roguelike · Action · Indie

BlazBlue Entropy Effect
Shared: Action · Action Roguelike · 2D

Rogue Legacy 2
Shared: Arcade · Action · Indie

The Binding of Isaac: Rebirth
Shared: Action Roguelike · Indie · 2D

Spelunky
Shared: Action Roguelike · 2D · Indie

EVERSPACE™
Shared: Action · Action Roguelike · Sci-fi

A Dance of Fire and Ice
Shared: Arcade · 2D · Indie

Brotato
Shared: Action Roguelike · Singleplayer · Sci-fi

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

Downwell
Shared: Action Roguelike · Arcade · Action

Streets of Rage 4
Shared: Action · 2D · Arcade

Halls of Torment
Shared: Action Roguelike · Action · Arcade

Dungreed
Shared: Action Roguelike · Action · 2D

Project Wingman
Shared: Action · Arcade · Indie

Exit the Gungeon
Shared: Arcade · Action · Indie

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

Have a Nice Death
Shared: Action Roguelike · 2D · Action