The phrase "active opponent" is correct and usable in written English.
It can be used to describe someone who is actively engaged in opposing or resisting something, such as a competitor in a debate or a rival in a game.
Example: "During the debate, she was an active opponent, challenging every point made by her adversary."
Alternatives: "engaged adversary" or "vocal challenger".
He was also an active opponent while a bishop in his native Argentina.
Talk story about a visit with Marcy Benstock, an active opponent of Westway since 1974.
In addition to a long and distinguished career in particle physics, Perl was an active opponent of military adventurism.
By metamorphosing into an active opponent of the Arab dictators, Erdogan reinforced the appeal of the "Turkish model".
A lifelong liberal, and active opponent of the Vietnam war, he was an individualist in a field – experimental particle physics – where large teams have become the norm.
The New Yorker, December 16 , 1985P. 32 Talk story about a visit with Marcy Benstock, an active opponent of Westway since 1974.
Factor 2, "active opponents", positions around actively opposing the practice of female genital cutting and considering the practice a violation of human rights.
Several union leaders said they would become extremely active opponents to the move, led by Mayor Michael R. Bloomberg, to reduce the role of political parties in New York City elections.
While on the surface ArcelorMittal like to appear a responsible company they have been very active opponents of climate change regulations in Europe.
Hundreds of the Kremlin's active opponents have left Russia in the last six years, moving the intellectual center of the opposition abroad, much as it happened in the seventies.
A spokesman for Crest Financial, a Clearwire shareholder that has been among the most active opponents of Sprint's offers, declined to comment.
