Slightly different take:
Batman can, conceivably, be defeated by criminals who are less skilled than 47, e.g. The Penguin, Two-Face, Scarecrow, etc. If these enemies stood no chance in hell against Batman, they’d be pathetic, sorry excuses for villains instead of the iconic arch-nemeses they are. The only reason they always lose to Batman in the end is because Batman is the hero of his story. Batman enjoys a narrative shield that I’ll call “the hero’s privilege”.
But, unlike Two-Face or The Penguin or Deathstroke, 47 is the hero of his own story. Like Batman, he enjoys the hero’s privilege – so when 47 fights Batman, we get something special: a fair fight.
And I believe that in a truly fair fight, 47 stands a chance. He’s still the underdog, but he has a chance.
Especially when you consider this:
In his canon, 47’s record is flawless. His win record is 100+/0.
Batman’s been beaten in one way or another several times. His back was broken by Bane, his mansion’s been burned to the ground, people who he’s tried to save have died, etc. etc.