The phrase 'most proficient in' is correct and can be used in written English.
You can use it to describe someone or something that is especially good at a certain activity or task. For example: "She is most proficient in Spanish, so she can help you with your Spanish studies."
The Rangers' power play, the most proficient in the National Hockey League, had five chances tonight but came up empty.
They are the stuff of skiers' nightmares, stopping even the most proficient in their tracks and leaving anyone still coming to terms with the sport quaking in their ski boots.
Nedved's absence had a dire effect on the Rangers' power play -- the most proficient in the National Hockey League this season -- as they were blanked on five man-advantage opportunities.
Although the unit based here is considered the most proficient in the country, allied officials said that it conducted 85 percent of its missions unilaterally, but still required coalition support for the other 15 percent.
Prodigiosin treatment proved to be the most proficient in inducing detectable PS exposure.
The researchers eventually surmise that botnet-cnc.rules are most proficient in detecting botnets.
The Prussian king Frederick William I (reigned 1713 40) had created perhaps the most proficient, if not the largest, army in Europe but had displayed no eagerness to use it except in the service of the empire, and then only reluctantly.
He has long been one of the most proficient drivers in racing, winning in every kind of series, from sprint cars to the elite Sprint Cup Series.
Microorganisms are the most proficient decomposers in nature, using secreted enzymes in the hydrolysis of lignocellulose.
In the backfield, the Jets had Curtis Martin, one of the most proficient backs in National Football League history.
A year on, Wales are the most proficient team in the Six Nations.
