Popular negatives

In the English language, the opposite meaning of many words are created by the addition of prefixes. For example :

• de : form / deform
• dis : able / disable
• il : legible / illegible
• im : potent / impotent
• in : direct / indirect
• un : true / untrue

If you observe carefully, the application of such prefixes are onto words that are generally in the positive sense. Adding the prefix makes them negative - happy to unhappy, pleased to displeased, practical to impractical and so on. There are not many inherently negative words that become antonyms by simply adding a prefix. Let's try out some :

Would un-ugly mean pretty?
Does dis-cheat mean we are being honest?
Or would im-messy clothes mean we are smartly-dressed?

There are however, a few words that break this convention. I was reading a news article the other day and realised that the reporter had used such a word. The word is - impeccable. Apparently, there is such a word as `peccable', which means `liable to sin or error'. Adding the prefix im- makes the word carry a positive meaning. Another example that comes to mind is `indefatigable', which in itself, is quite unique because it has double prefixes.

`Impeccable' and `indefatigable' also fall into another category which I'd like to call as `popular negatives'. These are words where the prefixed form are in more common use than the root form. Here are some examples, plus a sample sentence I've written using the base form of the word, and you tell me if I don't sound awkward  :

1. illicit : I passed through airport customs without any problems because I only carried licit goods in my baggage.

2. unscrupulous : I employed that young lady to handle the company accounts because of her scrupulous behaviour.

3. dismantle : I've lost the original instruction guide so now I don't know how to mantle all these parts back together.

4. incontinent : Of course these diapers are not for me, I'm continent!

I am sure there are other examples. Perhaps you know of some more. Enjoy the long weekend, my friends...