Is my worst enemy my best friend (interpreting negative adjectives applied to negative nouns)? [closed]

Don't confuse English language with the mathematical theory. The adjective worst qualifies the noun enemy with even more bad values. So, a worst enemy is more dangerous than a normal enemy.

The "science behind it" is pragmatics: if you use a word like "worst" you've almost certainly got negative thoughts around.

In principle you might be able to concoct an example of what you're suggesting, but I haven't managed to think of a way. What you can just about do is get "worst" to mean "least effective", as in

"I've ranked Batman's enemies in terms of how much trouble they give him. 
 The Penguin does best, and Catwoman is easily the worst"

but even there you need to set up quite a lot of context to avoid "worst" suggesting "nastiest".

[I'm not advancing the quote as an opinion, by the way: it's just an example!]