The phrase "formidable obstacle for" is correct and usable in written English.
You can use it to describe an obstacle that is difficult to overcome. For example, "Learning a new language can be a formidable obstacle for many people."
That's a formidable obstacle for a critic.
Anti-forensic tools, techniques and methods are becoming a formidable obstacle for the digital forensic community.
The creek, which was a formidable obstacle for either side to pass on our left, became a very slight obstacle on our right.
It's the worst gringo hypocrisy!" Hypocrisy or not, Colombia's negative reputation can pose a formidable obstacle for locals attempting to lure American friends to visit.
A central midfield built around the muscular Patrick Vieira, Gilberto and Edu – all athletes over six feet tall who were as comfortable protecting the back four as projecting the game forwards – was a formidable obstacle for any team trying to make inroads of their own.
As yet public opposition to GMOs, especially in Europe, might still be a formidable obstacle for such relaxation.
In consumer class actions, legal experts say, Microsoft has defenses that will lessen its potential liability and present formidable obstacles for plaintiffs.
Still, neither the settlement nor the law reduces the formidable obstacles for owners who want their property returned, or changes the fact that law-enforcement budgets can depend upon forfeiture revenue.
Those differences could create formidable obstacles for a president of either party, in the absence of a landslide like those that preceded creation of Social Security in 1935 and Medicare in 1965.
