Games like The Reaper Survivors
Games like The Reaper Survivors include Risk of Rain (2013), Risk of Rain 2, The Binding of Isaac: Rebirth, Enter the Gungeon, and Skul: The Hero Slayer. We matched them by the tags players give The Reaper Survivors on Steam (Action Roguelike, Idler, Perma Death, Roguelike, and 2D): closest matches first, and among equally close ones the better-known games.

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

Risk of Rain 2
Shared: Action Roguelike · Co-op · Roguelike

The Binding of Isaac: Rebirth
Shared: Action Roguelike · Roguelike · Pixel Graphics

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

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

Wizard of Legend
Shared: Action Roguelike · Roguelike · Pixel Graphics

Hero Siege
Shared: Action Roguelike · Co-op · Pixel Graphics

Vampire Survivors
Shared: Action Roguelike · 2D · Pixel Graphics

Ravenswatch
Shared: Co-op · Action Roguelike · Roguelike

Sephiria
Shared: Action Roguelike · Co-op · Roguelike

Children of Morta
Shared: Roguelike · Action Roguelike · Pixel Graphics

Streets of Rogue
Shared: Action Roguelike · Roguelike · Pixel Graphics

Gunfire Reborn
Shared: Co-op · Roguelike · Action Roguelike

Magicite
Shared: Roguelike · Action Roguelike · 2D

Nuclear Throne
Shared: Action Roguelike · Roguelike · Pixel Graphics

Roguelands
Shared: Action Roguelike · Roguelike · Co-op

Dead Cells
Shared: Action Roguelike · Roguelike · 2D

Noita
Shared: Roguelike · Pixel Graphics · Action Roguelike

Rogue Legacy
Shared: Action Roguelike · Roguelike · Action

Dungreed
Shared: Action Roguelike · Roguelike · Pixel Graphics

Heroes of Hammerwatch
Shared: Action Roguelike · Co-op · Pixel Graphics

33 Immortals
Shared: Action Roguelike · Co-op · 2D

Broforce
Shared: Co-op · Action · 2D

Rabbit and Steel
Shared: Co-op · Action Roguelike · Roguelike