The phrase "a big opponent" is correct and usable in written English.
It can be used to describe someone or something that is a significant rival or adversary in a competition or conflict.
Example: "In the championship game, we faced a big opponent that challenged our skills and determination."
Alternatives: "a formidable opponent" or "a major rival".
But he has been a big opponent in the past.
"I had a big opponent and a tough schedule that I couldn't deal with.
"We need to play against a big opponent to see where we are.
But you're a big opponent of people being lazy aren't you?
"A big win, a big opponent, a big match," said Mourinho.
Both lacrosse teams had chances to knock off a big opponent at home this weekend, but both came up short despite late rallies.
The wind had turned into a bigger opponent than the guy standing down the other end, and whoever kept his cool for just one more set would walk away with a Grand Slam title.
Chook Raper told me how once in a game against Newtown he was flattened by a bigger opponent and Pop Clay came over and said, 'Come on, get up!
Márquez, in a rare excursion beyond 140lb, knows the dangers of mixing it with a bigger opponent from his doomed catchweight contest against Floyd Mayweather Jr three years ago, and that admirable caution will inform his strategy again.
Capitalizing on what many saw as his genius for explaining America's psyche to itself, Pinsky began to focus on what he considered a bigger opponent, the disease that lay beneath them all: a toxic new form of narcissism, stoked by the media.
Barrie spun the suggestion into a masterful spoof on the British class system: Lord Loam scandalises polite society by inviting his servants to take tea with him once a month, though, as it turns out, no one is a bigger opponent of such social reversal than the butler Crichton – who extols the security and order of "a haughty English house".
