The phrase "real challenger" refers to someone or something that poses a genuine and strong opposition or competition to another person or thing. Full definition
His only real challenger for me was Francis Coquelin who was left with so much to do and produced some key tackles. (justarsenal.com)
With the arrival of Rayman Origins, Mario had his first real challenger in years. (goombastomp.com)
It's hardly a difficult call for us to make — the year - old Google Pixel C is its only real challenger at a similar size, and the Tab S3 replaces the now - cheaper, but still impressive Samsung Galaxy Tab S2. (techradar.com)