Games like Onion Assault
Games like Onion Assault include Pizza Tower, Tribal Hunter, Webbed, SANABI, and Katana ZERO. We matched them by the tags players give Onion Assault on Steam (Action, 2D Platformer, Platformer, Hidden Object, and Side Scroller): closest matches first, and among equally close ones the better-known games.

Pizza Tower
Shared: 2D Platformer · Platformer · Action

Tribal Hunter
Shared: Action · 2D Platformer · Platformer

Webbed
Shared: 2D Platformer · Platformer · Cute

SANABI
Shared: Action · 2D Platformer · Platformer

Katana ZERO
Shared: Action · Platformer · 2D Platformer

Oozi: Earth Adventure
Shared: 2D Platformer · Platformer · Action

Momodora: Reverie Under The Moonlight
Shared: 2D Platformer · Side Scroller · Platformer

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

Gravity Circuit
Shared: Action · Platformer · 2D Platformer

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

Grapple Dog
Shared: 2D Platformer · Action · Platformer

Super Meat Boy
Shared: Platformer · 2D Platformer · Indie

Prince of Persia The Lost Crown
Shared: 2D Platformer · Action · Side Scroller

Anomaly Agent
Shared: 2D Platformer · Side Scroller · Platformer

F.I.S.T.: Forged In Shadow Torch
Shared: Action · Platformer · 2D Platformer

20XX
Shared: Action · Platformer · 2D Platformer

Mighty No. 9
Shared: Action · Platformer · Side Scroller

Sonic the Hedgehog 4 Episode 1
Shared: Action · Platformer · Colorful

Spelunky 2
Shared: 2D Platformer · Platformer · Action

The Darkest Tales — Into the Nightmare
Shared: Platformer · 2D Platformer · Colorful

Lone Fungus
Shared: 2D Platformer · Action · Platformer

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

SHINOBI: Art of Vengeance
Shared: Action · 2D Platformer · Platformer

Broforce
Shared: Action · Platformer · Side Scroller