Seems to me that Prodigious has only one meaning -- "Remarkable in size, quantity, strength, etc."

And that is the only meaning; when used in a narrative it means horrible or wonderful entirely in the context of the usage. If I say that you have a prodigious office, I could be admiring you or be disgusted at your opulence; "prodigious" does not prescribe anything, the rest of my narrative must.

It is not a contranym like "liege". (Which is a wonderful contranym word, btw. I didn't know that it also meant vassal.)