below
Able, skilled, adept, capable, effective, and efficient.
Perform, conduct, begin
The word 'better' is a noun, a word for a superior person, thing, or state.Example: We're hoping that it's a change for the better.The plural noun, 'betters' is a word for people at a higher class of society than one's self.Example: Envy of your betters can lead you to foolishness.The noun form of the verb to better is the gerund, bettering.The word 'better' is the comparative form of the adjective good (better, best).The noun form of the adjective 'good' is goodness.
To be good at something could be proficient. To be bad at something could, therefore, be deficient. Deficient is an antonym for proficient.
I believe what you are looking for is term "Highly Developed" or "Exceptional." -Jubyloo
No it does not. Proficient means average, and advanced is advanced.
conversant
Applicants must be proficient in Microsoft Word and Excel. he's a highly proficient diver.
I am proficient in answering questions on wiki.answers.com
You could say "nonproficient"; "unproficient" isn't really a "word" (you can say it, but it's unusual).
effective.
able
capable
Excalibur is a much better word than exclaimed, in my opinion.
Even better!
Adept, proficient