Again for those who subscribe to threads, the issue has been resolved and the attack can be made. The character will just ignore the special attribute of the effect.

From the Player's Guide:

One thing I did not find resolved in this discussion, but it seems intertwined with it is:

Does a Colossal, such as Galactus or Dr. Manhattan, who ignores (penetrating)/psychic blast, ignore damage from Darkseid's Omega effect option 2?

OMEGA EFFECTS: Before Darkseid makes a ranged combat attack, you can choose any or all of the following options for the attack: 1) Darkseid's range value is halved and his line of fire ignores characters and hindering terrain; 2) Modify Darkseid's damage value by -2; damage from this attack is penetrating damage; 3) Darkseid's damage value is 0; if the attack succeeds, put the target in any unoccupied square within Darkseid's range to which he has a clear line of fire.

Thanks.

Penetrating damage, generally, is a game effect that describes damage that can't be reduced. Meanwhile, Penetrating/Psychic Blast or Exploit Weakness are specific powers that utilize that general game effect.

Just because a character might ignore or otherwise be immune to a specific power does not mean that it ignores the general game effect.