In the comic the only Transformer depicted in the same "cityformer" sense as the cartoon was Metroplex.

I don't recall either Fortress Maximus or Scorponok ever transforming into city mode. Fort Max's was shown in his Universe entry and he turned into battle station mode a few times (by the way it floats), but for all the comic book readers knew Scorponok only transformed into a scorpion.

Both were also only shown as tall Transformers. I know they rebuilt Fort Max to be bigger in his first main title appearance, but he was rarerly shown to be much bigger than roughly three times the average height in subsequent appearances.

Omega and Trypticon were also both shown as very big robots in their comic debuts but seem to shrink in subequent appearances (particularly Omega). Did Trypticon turn into city mode in "King of the Hill"? I only recall the battle station.

Metroplex however in his one and a page issue appearance was a giant robot (698 feet tall) but as Skyshadow mentioned his city mode was never toy-accurate and was instead shown to be Autobot City: Earth. (And that was actually more of a Pretender Shell).

Comparing characters like Scorponok and Metroplex from the comic point of view really doesn't make much sense.

So you need to approach this soapbox from STL's admitted cartoon biased perspective.

Althought that does kind of rule out Overlord too which means it's more a toy thing... which if I was just going by toys I would vote Fort Max.