Specifically I'm looking for an antonym of the infinitive rather than the noun. For example, "fragrance" is an antonym of "stink" (the noun), but you can't say "Wow, that fragrants" or "Wow that fragrances" in the way you can say "Wow that stinks".
I don't think there's a single verb available in English which is the exact opposite of "To stink". With exact opposite I mean as in that it can be used the same way with opposed-meaning sentences (like "I love you" vs "I hate you").
On my NOAD I found this example "That's a lovely scent you're wearing". There is also the expression "to smell good", although I guess (since I'm not a native speaker) they may not fit all situations and contexts, as in formal/informal, so about this I'd like some native speaker to give contribution.
Finally, I found to perfume, which means "to make the air in a place smell pleasant", but I didn't suggest this one because it's especially used with flowers as in "The garden was perfumed with the smell of roses."
If I find more, I'll make sure to include it.
I don't think there is a single English verb meaning to give off a pleasant fragrance in common parlance. This may be partly because of vagueness surrounding the word smell itself, which is of unknown origin.
Unless modified by a positive adjective, the default meaning as both verb and noun is invariably negative. The unmodified "You smell" always implies "bad". So even though you might think there's an intransitive verb to smell meaning to give off a (good / bad / neutral) aroma, that's not really true. The core meaning is negative - it's just that you can reverse it with positive modifiers.
The standard expressions are smell nice, be fragrant, etc. Any single word would be at the very least uncommon and potentially unfamiliar to the hearer. So I think even if there was such a word, I at least would be wary of using it lest the negative connotations from the associated usage of smell caused my intended compliment to backfire.