OK, on to Anty’s abilities.
Deities and Demigods said:
He grows stronger each round he fights, as long as he remains on the earth. Antaeus starts similar to a hill giant in size and appearance, but every round he fights he grows, gaining the size and strength each round of the next largest giant type, until he reaches titan strength and size.
Antaeus will remain at titan size as long as he fights, gradually shrinking when the battle is over.
What I originally wrote:
Growth (Su): Every round that he is in combat after the first one, Antaeus continues to grow and become stronger. After each combat round, he grows two feet taller (and appropriately heavier), increases the damage on his slam attack by 1d8, and gains 2 points of Strength and Constitution, with appropriate damage and hit point adjustments. He continues to grow until he is strong like a titan: 23' tall, with Str 37 and Con 29, with a slam attack of 8d8+15 damage. Antaeus will remain at this size as long as he fights, and will gradually shrink back down to normal size when the battle is over.
That is a bit of a messy explanation though. What can I say; that was four years ago and I was definitely not well-practiced.

if he is only going up to titan size, that is not much bigger than what he started out with isn't it? It meant more in 1E I think.
Let me go out in a limb here, and do something I don't often do: how about just going with the most simplest explanation and say he just grows one size category every time he grows and let him go all the way to Colossal? This would give him the Str, Con, nat armor, and other bonuses, as well as increase the base damage he deals with weapons.
We could say that, perhaps, his height doubles every round, or maybe the change would be every other round.
Deities and Demigods said:
Each time he grows, all damage he has taken is healed, and he increases a further 25 hit points (up to 250 total). Even after he ceases growing, all damage he takes in one round is healed in the next as long as he remains on the earth.
What I originally wrote:
Regeneration (Su): Antaeus heals all damage practically instantaneously at the beginning of each round. When his hit points increase at the beginning of a round, he will therefore have his new maximum hit points.
Probably call it a derivative of fast healing, but I'm sure it would otherwise be the same, rewording it as necessary.
Deities and Demigods said:
If Antaeus is lifted off the ground, he loses strength and size at the same rate he gained it, and will no longer heal.
What I originally wrote:
Contact With Earth (Su): Antaeus must maintain contact with the earth in order for his powers to function. If he is somehow lifted off the ground, his regeneration will no longer work (although he does not lose hit points that he had gained because of it), and he will return back to normal size at the same rate at which he grew.
Again, should stay pretty much the same but reworded.