The phrase "a formidable machine that" is correct and usable in written English.
It can be used to describe a powerful or impressive machine, often in a context where its capabilities or features are being highlighted.
Example: "The engineers unveiled a formidable machine that could revolutionize the manufacturing process."
Alternatives: "an impressive device that" or "a powerful apparatus that".
Describing the church as a "formidable machine" that had blocked any investigation, one told the Observer: "The abuse we received at the hands of Keith O'Brien is dwarfed by the systematic abuse we have received from church officials.
It was largely because of Ms. Guerrero -- and hundreds of other college students like her across the country -- that Mr. Obama assembled a formidable machine that helped him roll to victory in 2008, a triumph that included putting Nevada into the Democratic column for the first time in 12 years.
But Sullivan Chen, an engineer from Verizon who assisted the 22-member Bay Shore High School's ET team with the Mechanical Marauder, a formidable machine that resembled a tank and could collapse to 12 inches or extend to nine feet with a metal claw, said the inequity between teams mirrored real life.
Osborne worried about Straw's inexperience and Labour pedigree, although he joked that he was not about to complain if Mandelson could recreate and put at his disposal the formidable machine that had carried Tony Blair to three consecutive election victories.
He has also built a formidable machine in the states that get the political season off to a start.
But Mrs Clinton still has a formidable machine behind her.
"We're facing a formidable machine and they are working harder than they did for Denis Butler," Mr. Thermos said.
But he had a formidable machine and no one wanted to be the first to break ranks and challenge him.
On paper it's a formidable machine.
Philip did an amazing job bulding Beenz into a formidable machine with a market value in the hundreds of millions.
They are patriots, trying to help Palestinians defend themselves from the onslaught, this formidable military machine that has been unleashed.
