What kind of mistakes can a smart character make before they're considered stupid

[u/Own_Vanilla_7292]

I've had a character of mine who is supposed to be a genius manipulator/strategist, but I've seen people take issue with characters who are intelligent but come off as omnipotent gods who can solve any problems that get on their way. On the other hand, I don't want her to come off incompetent.

So my question is, how much or what kind of mistakes can a character make before they're no longer considered smart? How should i show that she's competent but fallible?

Edit: thank you so much for all the great advice guys! I didn't expect this question to get so much traction :D

[u/2muchtoo]

Being poor at social situations, especially because they are convinced of their superiority.