Seems like none of them are really dumb.
1 seconds sound clip from the 18 Bronze Girls of Shaolin (1983) movie soundboard.
You can hear this line at 00:55:41.700 in the DVD version of the movie.
Quote context
[...]
- I've been checking on them. They're among that gang of dumb women that put on disguises, sir.
- What's that? Is that part of Pia Fine's gang?
- No, sir. That's another group.
- God damn it! Just how many of these dumb women gangs are we up against?
- I'm just as confused as you.
- I can't trust you to do anything right, you useless fool.
- Seems like none of them are really dumb.
- I've no idea who's really dumb and who isn't. They're driving me mad.
- Now if you can manage to succeed this time, you can marry all 18 bronze girls if you want.
[...]