fairly common usage

also written as arch-charlatan
or arch charlatan, which I think is incorrect

and an archcharlatan from Egypt who insisted on being addressed as Doctor

in this case, because it seems to concern a person who passes himself off as a doctor, I would prefer "charlatan"or "quack"

charlatan - someone who pretends to have special skills or knowledge - used to show disapproval (Longman)

quack - someone who pretends to be a doctor - used in order to show disapproval (Longman)
quacks selling weight-loss drugs

VDale charlatan -
1) kwakzalver, beunhaas, oplichter
2) opschepper, windbuil, praalhans

Een charlatan is een speciaal soort oplichter die voorziet in zijn behoeften door systematisch mensen te bedriegen over zijn afkomst, vaardigheden, intenties of prestaties. Een charlatan maakt gebruik van zijn charme. Het woord wordt ook wel gebruikt voor mensen die zonder zelf de bewuste intentie te hebben te misleiden ideeën of denkbeelden presenteren die zij zelf voor waar houden maar die de wetenschappelijke toets der kritiek niet kunnen weerstaan. In de geneeskunde spreekt men dan vaak van kwakzalverij.

http://nl.wikipedia.org/wiki/Charlatan

A charlatan (also called swindler or mountebank) is a person practising quackery or some similar confidence trick in order to obtain money, fame or other advantages via some form of pretence or deception.

The word comes from French charlatan, a seller of medicines who might advertise his presence with music and an outdoor stage show. The best known of the Parisian charlatans was Tabarin, who set up a stage in the Place Dauphin, Paris in 1618, and whose commedia dell'arte inspired skits and whose farces inspired Molière. Ultimately, etymologists trace "charlatan" from either the Italian ciarlare, to prattle; or from Cerretano, a resident of Cerreto, a village in Umbria, known for its quacks

http://en.wikipedia.org/wiki/Charlatan

charlatan, however, is only half the job, for what could be a translation for "rasoplichter" if he is a "rascharlatan" ?

I think "archcharlatan" does the trick

I'll give you a few examples as well

Keith is portrayed as the archcharlatan, a man of willpower and determination, sly, witty, without moral scruples, utterly self-centered

http://www.wordnik.com/words/archcharlatan

Fabulous long excursion through the follies of the Earf Day minions. Your essay on Sendler and the accompanying one from American Thinker inspire, yet also make the blood boil (and not from Global Warming). I like to think of the warming the Nobel Committee and archcharlatan Gore will be feeling as they spend eternity in Hell for their shoddy treatment of Irena Sendler

http://vocalminority.typepad.com/blog/2009/04/its-earth-day-...

But such a result, desirable as it might be, can hardly be expected soon, for these remarkable records, the archives of a bygone era and of a race long since vanished from the earth, are in the possession of the archcharlatan of our century; and the only result that can be reasonably anticipated from his pretended translation of these hieroglyphics is another delectable little book, something like the 'Book of Mormon,' only perhaps even more absurd and ridiculous than this is!

http://en.wikisource.org/wiki/St._Louis_Gazette/May_18,_1844

On the night of December 23, 1913 the United States Congress passed the Federal Reserve Act and thereby committed the greatest act of TREASON in history. It surrendered this nation's sovereignty and sold the American people into slavery to a cabal of arch-charlatan international bankers who proceeded to plunder, bankrupt, and conquer this nation with a money swindle

http://crooksandliars.com/2008/03/17/fed-cuts-rates-by-a-qua...

Interesting discussions so far about the possible translations, but I like to keep things simple for a word like this. "true" or even "pure" would work for the prefix ras-
As for "oplichter": plenty of choices there.. swindler, sharper, crook, con-man, ... take your pick ;)