There are many great units in ALS, but Baldy is definitely one of the best choices because he is a Hybrid unit. Check out how to get Saitama in Anime Last Stand and all of Baldy's stats and upgrades that will help you gain levels.
The INSANE start from Noob to Pro in Anime Last Stand (Roblox)
Saitama is a Celestial unit that you can obtain from Banner 2 in the summoning area. To unlock Banner 2, you must first unlock Planet Namek levels in Story mode. Once you complete it, the banner and all Celestial units will be available to you.
You have a 0.5% chance of getting Saitama, which is pretty low, so you'll definitely want to farm Emeralds ahead of time. You want to have at least enough to get the Celestial pity, which is at 250 pulls.
Related: How to Evolve Gojo in Anime Last Stand
