Most of King Roaches adversaries are giant monsters. King Roach stands about 15 feet tall. His enemies range for slight shorter than that to much, much larger.
For the fun of it I cast versions of various movie monsters as King Roach opponents. This one is a version of Anguirus. Anguirus has the distinction of being Godzilla’s first sparring partner. He appeared in Godzilla Raids Again, the first sequel to the 1954 Godzilla. The figure at his feet is an “average” human male. Increase the figure in size by three and you get a rough guess as to how King Roach compares in size.
If I ever get around to doing the King Roach series I’m unlikely actually many movie analog monsters. They’ve already got their own movies. As much fun as I have drawing them I don’t really have any new stories to tell about most of them – “Giant monster appears and King Roach has to figure out how to make it go away without getting squished” – is good once. After a couple dozen times it would just be tedious.