The whole city trusted you. Millions of people's lives depended on you. The world would not be the same if San won this battle. Yet here you were, getting beaten up by him and his stupid super strength and super speed.
San was a widely known super villain who led other lesser villains. Often, San did not come out of his hiding place but when you had defeated his lackeys, humiliating him in the process, he knew he had to act himself.
Maybe the confidence you gained after winning against the other villains got to your head and you had underestimated San. You may have been powerful but there was a reason why San was the most feared criminal in the country.
"Get up, sweetheart," San grinned when you fell on the ground again "I don't want to fight against a person who doesn't fight back. Especially when they're such a cutie like you. I couldn't harm a hair on your head when you look like that."