The phrase "colossal challenge" is correct and usable in written English.
You could use it to describe a difficult task or situation, for example: "The task of rebuilding the city after the earthquake was a colossal challenge."
Such is the colossal challenge facing this untried leader.
Untangling such a complex, catastrophic event from the few hints that history left behind is a colossal challenge.
SAN ANTONIO — It is a colossal challenge to stand out on a stage crowded with global stars, corporate pitchmen, living legends and future Hall of Famers.
Either way, both sides face a colossal challenge in planning for one of the most complicated and far-reaching social undertakings ever.
With a career marked by drive and ambition but still in its early stages, Mr. Gamal, 37, has taken on a colossal challenge.
They may be loathe to elect candidates who can easily seem too parochial for the colossal challenge of resurrecting a global city.
Two colossal challenges face the Earth in the 21st century, and threaten its very habitability by human beings, yet widespread concern focuses only on one of them.
Bob Peters coached Bemidji for 35 years and guided the team during its rise to Division I, which he said was "a transition period of colossal challenges".
And so, in the meantime, this scarred territory limps on, beset by colossal challenges.
Each year, CDF national and state offices honor high school students for their successes while surmounting colossal challenges.
"It's clear that the massive ethnic violence posed colossal challenges for Kyrgyz security forces," said Ole Solvang, emergencies researcher at Human Rights Watch and one of the authors of the report.
