Look up the word curbstomp, then invent the nuclear powered version.
Galactus is just too powerful, with the Silver Surfer aiding him, the odds become even more unsurmountable!
I'm uncertain if anyone from DC can match Galactus in terms of raw power, let alone technological brilliance.
To give you an idea, Galactus once defeated 20 of the most powerful superhumans on Earth and the Infinity Watch just by pressing a button on his ship (it fired a ray that paralyzed everyone it hit).
The Silver Surfer could possibly be matched, but the Power Cosmic that sustains him is quite formidable, I'm uncertain if there is a DC character that can match that.
He's also one of the most powerful Heralds of Galactus, only one other has surpassed him.