Games like Alter World
Games like Alter World include LIMBO, Defy Gravity Extended, Braid, Hollow Knight, and Hollow Knight: Silksong. We matched them by the tags players give Alter World on Steam (Indie, Puzzle, Puzzle Platformer, Platformer, and Difficult): closest matches first, and among equally close ones the better-known games.

LIMBO
Shared: Indie · Puzzle Platformer · Puzzle

Defy Gravity Extended
Shared: Indie · Puzzle Platformer · Puzzle

Braid
Shared: Puzzle · Puzzle Platformer · Indie

Hollow Knight
Shared: Platformer · Indie · Difficult

Hollow Knight: Silksong
Shared: Indie · Difficult · 2D

Squishy the Suicidal Pig
Shared: Indie · Puzzle · Platformer

Celeste
Shared: Indie · Difficult · Platformer

Out There Somewhere
Shared: Indie · Platformer · Puzzle

FEZ
Shared: Puzzle · Indie · Platformer

Cuphead
Shared: Difficult · Platformer · Indie

Nihilumbra
Shared: Indie · Puzzle · Platformer

ANIMAL WELL
Shared: Puzzle · Puzzle Platformer · Platformer

Teslagrad
Shared: Puzzle · Indie · Platformer

Geometry Dash
Shared: Difficult · 2D · Platformer

Toki Tori
Shared: Indie · Puzzle · Platformer

Baba Is You
Shared: Indie · Puzzle · Difficult

Super Meat Boy
Shared: Indie · Platformer · Difficult

I hate this game
Shared: Indie · Puzzle · 2D

Portal 2
Shared: Puzzle · Platformer · Puzzle Platformer

BADLAND: Game of the Year Edition
Shared: Indie · 2D · Platformer

BEEP
Shared: Indie · Platformer · Puzzle

Rain World
Shared: Indie · Difficult · Platformer

La-Mulana
Shared: Indie · Platformer · Difficult

Munin
Shared: Indie · Puzzle Platformer · Puzzle