To be fair, the main character was a pretty powerful Dragon Slayer that used to go toe to toe with Dragons trained for war before getting captured by the Silver Dragon Queen. This guy is probably more powerful than most other dragons, but ultimately relies too much on his natural talent as a noble, meaning he's nothing compared to better trained individuals. He also thought he was up against a commoner level dragon that wouldn't normally be so strong and was thus caught off guard when his opponent proved to be much more capable than expected. I imagine the situation is like an intermediate and talented martial artist challenging some that seems to be a beginner, only to find out they're a master 🤔