Ok, just doing this cos I’m bored (and I also just finished reading Galactus: The Devourer lol). Dunno if anyone has already done a speculative thread on Galactus, but he’s my favourite cosmic badass (sorry Thanos and Beyonder), so yea.
NB: Galactus’ powers assume that he will never be playable by us mere mortals, ie he can only be faced in a boss mode, kinda like Gorgon and Ultron. Hence there is no concept of his skills improving with an increasing number of covers, unlike everyone else (bar the two aforementioned bosses). In other words, his abilities are the same in terms of effects, whether at 1/1/1 or 5/5/5. The only difference is damage done; other effects, like AP steal and number of special tiles remain constant throughout. So technically speaking, Galactus can only always be at 5/5/5. No other build is possible.
Galactus (The Devourer)
(Imba Character)
Infernal Hunger (passive)
Galactus’ insatiable hunger results in his consuming worlds without a care for any forms of life. Steals 1 AP of every colour at the start of every turn. If Galactus has at least 6 AP in at least 3 colours including 
, this power becomes Cosmic Strength instead.
Galactic Force Field (14 AP)
Galactus throws up a force field to protect himself while he is busy feeding. Creates 3 strength 104 Blue Protect tiles. If a Protect tile is destroyed in any way, Galactus retaliates, dealing 2175 damage and creating a strength 159 Blue Strike tile.
Power Cosmic Rage (15 AP)
Using the same technology that created the Silver Surfer, Galactus unleashes his full might on those who would dare oppose him, dealing 4275 damage to the enemy team and destroying 6 random tiles, dealing damage and generating AP.
Cosmic Strength (6 AP)
Having eaten (some of) his fill, Galactus displays his might, dealing 1219 damage to the enemy team and replenishing himself for 1073 health. This exertion costs Galactus 2 AP in every colour.