Giant-man vs Superman

Giantman is given the ability to grow as much as he wishes and is placed in an alternate universe to grow as much as he needs to. He then must punch Kalibak with the same strenght that a non-holding back Superman would muster.

How much does Giantman needs to grow to equal Superman's punching power?

How much does he needs to grow to one-hit Superman (who won't defend)?

Giant man's inertia would surpass his strength. He wouldn't be able to move.

Physics be damned, in this thread the LT makes Giantman able to move as he would in other condition respecting the strength he gets by growing and other non-sensical comic stuff.