The phrase "a series of formidable" is correct and usable in written English.
It can be used to describe a collection of impressive or powerful things, often in a context where their strength or impact is being emphasized.
Example: "The conference featured a series of formidable speakers who captivated the audience with their insights."
Alternatives: "a number of impressive" or "a collection of powerful".
Translating advances in the laboratory into sound clinical practice presents a series of formidable conceptual and technical challenges.
But the expansion faces a series of formidable hurdles if it is to be delivered on schedule by 2018-2020 – and may never be built.
The appeals court also refused to entertain the government's objections to a series of formidable hurdles to a conviction put in place by the trial judge.
Second District, Eastern Connecticut: During his 20 years in Congress, Representative Sam Gejdenson has faced down a series of formidable challengers, not unlike this year's opponent, Robert Simmons.
As the 2018 nomination season gets underway, analysts anticipate a network of insurgent candidates and activists to seek a liberal purification of the Democratic Party, in the same way that Tea Party members took aim at a detested Republican "establishment" via a series of formidable primary challenges and congressional leadership battles.
During the deliberation I watched, he and bailiff Beth Stelling tear that rule to shreds with a series of formidable rips from a camera-friendly if somewhat goofy—bong. .
The latter poses a series of particularly formidable technical challenges, but if the past is any guide to the future, then we can expect optical dating to illuminate much more of human history before celebrating its Golden Jubilee.
Comaneci earned the sport's first perfect ten, and was followed by a series of equally agile but formidable girls who dominated the sport, many of them tutored by Comaneci's coaches, Martha and Bela Karolyi.
Each book involves a series of challenges for Reacher's formidable powers of deduction.
A series of incredible results against more formidable opponents, including a victory against Haiti, led Antigua and Barbuda to the semifinal round of qualification for the first time.
Living in a small home with a decidedly rural feel at Wymondham, Sebald wrote a series of books which made him a formidable critic of German writing, including studies of Sternheim, Doeblin, the German theatre, and two collections of essays on Austrian writing.
