The following comic characters are noted for unusual and/or prolific consumptive feats. Which, in your opinion, is most formidable as either an opponent or in an eating contest, relative to size or on an absolute scale, and why?
Believe it or not, in his early days, Lobo once compressed and then swallowed a city in one bite. I'm nearly 100% certain that feat has been retconned, and I declined to post it, 'cause it's not all that kid-friendly, but you can find it easily enough by visiting most any Lobo respect thread.
2. Good find, Riv! Consumption of the Miracle Machine was exactly the showing I was thinking of for old-style M.E.Lad. I've always wondered what happened to he and Braniac after that storyline, but I've never discovered the answer. Even that particular issue I'm told never had a reprint and is difficult to find. I presume someone was clever enough to help them both "get better" at some later point in the series, though. Can't imagine that would have been the final issue for either character.
My vote would have been for Thanos for obvious reasons, but since he's not on the list, I have to go with Galactus:
Galactus was instrumental in the defeat of the Annihilation Wave and defend the Universe on more than once occasion. He defeated Tyrant when even Thanos, Silver Surfer, Jack of Hearts, Gladiator and other power houses were unable to.
Galactus destroyed the Ultimate Universe and subdued "Gah Lak Tus" who was virtually unstoppable in its respective universe.
Galactus has been one of the few entities to survive direction assaults from the Phoenix Force for the longest period of time.
Galactus was able to infiltrate the Realm of Aggomoto to retrieve Dr. Strange during the Infinity War.
He is supposed to be a Universe-Level Powerhouse, but his influence extends beyond one universe. In proportion to his place in the cosmic hierarchy he has been most impressive in my opinion.