here's a topic that has come up here not infrequently in the past. I was reminded of it today when I came across the phrase "stinting in the extreme" -- stinting is outGoogled by unstinting by nearly an order of magnitude.

but this isn't really why I've come here tonight. I'm wondering if we ever came up with a term for these "Words better known in their negative forms"? I'm not really looking for a neologism, just curious if there already exists a philological term for this.

Quinion has called extreme examples of these "unpaired words".
http://www.worldwidewords.org/articles/unpaired.htm