The phrase "a string of formidable" is correct and usable in written English.
It can be used to describe a series of impressive or powerful things, often in a context where you are highlighting their strength or significance.
Example: "The team faced a string of formidable opponents throughout the tournament, each more challenging than the last."
Alternatives: "a series of impressive" or "a chain of powerful".
Savitt's jump is the latest in a string of departures at Yahoo, the once-formidable search giant that, under the leadership of Marissa Mayer, has been in the midst of a big turnaround plan to claw back revenues and market share in the face of competition from the likes of Google.
Dolly Parton Halos and Horns (Sugar Hill Records) **** Since 1998, Dolly Parton has been enjoying a formidable creative streak, collecting a string of Grammys along the way.
How could the addition of music possibly enhance a play that unfolds so effortlessly as a string of classic one-liners, including those proclaimed by the formidable Lady Bracknell?
The formidable persona she crafted also earned her a string of unflattering nicknames, such as "Attila the Hen" and her best-known moniker, the "Iron Lady".
The victory capped what historians call the 10 crucial days of the American Revolution, in which Washington reversed a string of bitter defeats and went on to transform the Continental Army into a formidable fighting force.
The Israeli government tightened its already formidable blockade of Palestinian cities and villages, after a string of terrorist bombings that has left at least 25 dead in less than two days.
David Boies, the formidable trial lawyer working for the government, has eviscerated a string of top Microsoft executives on the stand.
On one wall hangs a formidable assortment of inky cast-iron skillets; on another is a string of garlic that the Greniers brought back from France, where they have a summer house.
What follows is a string of impressionistic reminiscences — of a gentlemanly pervert in Kentucky, a self-absorbed lover in New York, a formidable washerwoman in Maine, a philandering doctor in Amsterdam.
Contemporary portraits show a formidable but straight-backed king who hacks his way to the throne through a string of murders including his nephews, the little princes in the tower.
