RIO DE JANEIRO — The last hope for Cameroon to win a 2016 Olympic medal arrived in the wrestling arena on Thursday night in the stern and determined form of Annabel Laure Ali, a 31-year-old who would vie for a bronze in the women’s freestyle competition. Gladiatorial rock music blasted from loudspeakers as Ali walked to the mat a few feet behind her opponent, Ekaterina Bukina of Russia.

It had been a tough Olympics for this Central African nation of 22 million. The news media in Cameroon belittled the performance as “Operation Zero Medals.” By Thursday, at 5 p.m., only Ali could save the country from an Olympic shutout.

“I win, I lose,” she had said in an interview about pressure a few hours earlier. “I don’t want to regret after.”

For all their egalitarian aspirations, embodied by the parade in the opening ceremony, the Olympics are a highly lopsided affair. Through Saturday afternoon, the five most victorious countries had claimed nearly 40 percent of all the medals, and the top 10 owned about 55 percent.