Games like Giga Girl
Games like Giga Girl include Freedom Planet, Shovel Knight: Treasure Trove, Broforce, Celeste, and Hollow Knight: Silksong. We matched them by the tags players give Giga Girl on Steam (Action, Indie, Platformer, Female Protagonist, and Retro): closest matches first, and among equally close ones the better-known games.

Freedom Planet
Shared: Action · Platformer · Female Protagonist

Shovel Knight: Treasure Trove
Shared: Platformer · Indie · Retro

Broforce
Shared: Action · Platformer · Indie

Celeste
Shared: Indie · Platformer · Female Protagonist

Hollow Knight: Silksong
Shared: Indie · Platformer · Female Protagonist

ICEY
Shared: Action · Female Protagonist · Indie

Bright Memory: Infinite
Shared: Action · Female Protagonist · Indie

Katana ZERO
Shared: Action · Platformer · Indie

The Messenger
Shared: Platformer · Retro · Indie

Bloodstained: Curse of the Moon
Shared: Action · Platformer · Retro

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

Planet of Lana
Shared: Action · Female Protagonist · Platformer

Bleed
Shared: Action · Indie · Platformer

Angry Video Game Nerd Adventures
Shared: Indie · Action · Platformer

Defy Gravity Extended
Shared: Indie · Platformer · Action

Gato Roboto
Shared: Indie · Action · Platformer

Iconoclasts
Shared: Indie · Action · Female Protagonist

Dust: An Elysian Tail
Shared: Action · Platformer · Indie

Indivisible
Shared: Indie · Action · Female Protagonist

Out There Somewhere
Shared: Platformer · Indie · Action

Gravity Circuit
Shared: Action · Indie · Platformer

Hotline Miami
Shared: Action · Indie · Retro

Super Meat Boy
Shared: Platformer · Indie · Retro

Axiom Verge
Shared: Indie · Platformer · Action