Games like Diamond Thief
Games like Diamond Thief include Katana ZERO, SANABI, Pizza Tower, Celeste, and Super Meat Boy. We matched them by the tags players give Diamond Thief on Steam (Action, Platformer, 2D Platformer, Pixel Graphics, and Singleplayer): closest matches first, and among equally close ones the better-known games.

Katana ZERO
Shared: Action · Pixel Graphics · Platformer

SANABI
Shared: Action · Pixel Graphics · 2D Platformer

Pizza Tower
Shared: 2D Platformer · Platformer · Indie

Celeste
Shared: Pixel Graphics · Platformer · 2D Platformer

Super Meat Boy
Shared: Platformer · 2D Platformer · Pixel Graphics

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

Gravity Circuit
Shared: Action · Platformer · Pixel Graphics

VVVVVV
Shared: Platformer · Pixel Graphics · 2D Platformer

The Messenger
Shared: Platformer · Pixel Graphics · Action

Rogue Legacy
Shared: Platformer · Action · Indie

Shovel Knight: Treasure Trove
Shared: Platformer · Pixel Graphics · Action

NINJA GAIDEN: Ragebound
Shared: Action · Platformer · 2D Platformer

Broforce
Shared: Action · Pixel Graphics · Platformer

Super Bernie World
Shared: Action · 2D Platformer · Indie

Downwell
Shared: Pixel Graphics · Platformer · Action

Himno
Shared: Platformer · Pixel Graphics · Singleplayer

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

Sonic Origins
Shared: Action · 2D Platformer · Platformer

Azure Striker Gunvolt
Shared: Action · Platformer · Indie

Planet of Lana
Shared: Action · 2D Platformer · Platformer

BlazBlue Entropy Effect
Shared: Action · Platformer · Pixel Graphics

Out There Somewhere
Shared: Platformer · Pixel Graphics · Indie

MO:Astray
Shared: Action · Indie · Pixel Graphics

Ambidextro
Shared: Action · 2D Platformer · Pixel Graphics