Positive adverbs for negative verbs?
Solution 1:
In At Dawn We Slept, Gordon Prange's definitive work on Pearl Harbor, he has some excellent quotes from military men with strongly expressed opinions.
I recall one of them describing a colleague as perfectly useless. So it's definitely possible to use these expressions idiomatically, especially in a context where "negative" things like weakness or isolation are seen as desirable by an attacker, or by people whose thoughts run along these lines.