The phrase "a decisive figure" is correct and usable in written English.
It can be used to describe someone who plays a crucial role in a situation or decision-making process.
Example: "In the negotiations, she emerged as a decisive figure, influencing the outcome significantly."
Alternatives: "a key player" or "a pivotal character".
From the reporting that I've read, he may have been a decisive figure.
Javier Solana, who was NATO's secretary general, is also portrayed as a decisive figure who tried to rally support in Europe for the bombing.
The rest are about evenly divided between those who say their vote will be motivated by their desire to express support for the president and those who want to voice opposition to him, suggesting that Obama might not be a decisive figure in the contest and that the race is not the early referendum on the Obama presidency many have suggested it would be.
Schlegel had an outstanding knowledge of art, history, literature, architecture, anthropology and foreign languages, which made him a decisive figure in the early development of comparative literature and modern linguistics, and with the creation of the journal Indische Bibliothek, he inaugurated the domain of Sanskrit studies in Germany.
Most Egyptians regard him as a decisive figure who can end the political turmoil that has gripped Egypt since a popular uprising backed by the military toppled autocratic president Hosni Mubarak in 2011.
At a time when many Indonesians "yearn for a decisive figure akin to Suharto, Prabowo is seen as a return to a stronger, more straightforward Indonesia," says a former high-ranking official in Indonesia's Corruption Eradication Commission.
Just like forgetting this incredible scene from his childhood when his father, a complex, decisive figure, ordered him to commit suicide were he to fail.
He rediscovered his touch with the bat - passing 70 in three of his last four innings of the series, although still searching for that elusive hundred - and became a markedly more relaxed and decisive figure both on and off the field.
But there must also have been a sense of vindication, of relief at having been the decisive figure in the second leg after having been so innocuous in the first.
Deng was the decisive figure in the reform.
Phil Davis had claims to being the most decisive figure on Saturday afternoon at the MCG.
