First off, STTGL is not the size of hundreds of universes. He's about half the size of our universe, and his drill is whats the size of approx. 100 universes. Regardless, he would effortlessly kill Galactus in this form. Go outside, and find a gnat, and crush it in your hands.
From STTGL's perspective, Galactus would be the gnat.
Galactus fully fed is typically around universal. STTGL is significantly beyond that.
"Why is everybody so ****ing stupid?"- Kim Jong Il, Team America.