weak part
weak spot
soft spot

That was one of several weak spots in his character.

This is less a real station than just a security post for a weak spot.

At the same time, judges are a weak spot of the party.

And she kept trying to find a weak spot in the walls.

It found a weak spot in the building wall, and the whole front of the structure gave.

They were looking for weak spots to work on later.

He began looking for a frank or a weak spot, trying to make some sense of the battle.

So I decided to get you at your weak spot.

We went from one to another, looking for a weak spot but finding nothing.

So far, they didn't seem to have any weak spots.