The phrase "a powerful example that" is correct and usable in written English.
You can use it when introducing a specific instance or case that strongly illustrates a point or argument you are making.
Example: "The recent climate report serves as a powerful example that urgent action is needed to combat global warming."
Alternatives: "a compelling illustration that" or "a strong case that".
"CVS Caremark sets a powerful example" that will help bring down health care costs and save lives, stated President Obama, a former smoker.
Secretary Clinton set a powerful example that should be heeded by world leaders as well as our policymakers here at home".
She set such a powerful example that, as her biographer Blanche Wiesen Cook pointed out in a recent interview, Lucy Mercer began to model herself after Eleanor, taking political interest in a way she hadn't before and ardently supporting integration.
It is an issue of food quality as well, and a powerful example that the global food chain is a complicated and messy affair.
It's an amazing example of human evolution probably the most powerful example that's ever been demonstrated of resistance to lethal infection".
In 2010 it was described by The Guardian as "far and away the most powerful example that I've experienced in this country of how and why opera can still matter".
It's one thing to hear people say, "It's different for us," it's another to read powerful examples that will stick with you forever.
Gomorrah is a powerful example of that thrilling current of energy which right now is lighting up Italian cinema.
"Public art can provide a new way to experience the city, and the Waterfalls were a powerful example of that," says Susan K. Freedman, president of the Public Art Fund in New York City, which worked with Eliasson on the project.
Former smoker President Obama applauded CVS, saying the company "sets a powerful example" and that its decision "will have a profoundly positive impact on the health of our country".
The ties that bind the Israelis and the Palestinians — in his words, two peoples "destined to live together on the same soil" — are a powerful example of the connections that tie us all together across the globe.
