un ‧ der ‧ bel ‧ ly /ˈʌndəˌbeli $ -ər-/ BrE AmE noun [singular] literary
1 . the unpleasant parts of a place or society that are normally hidden
underbelly of
photographs that capture the underbelly of the United States – its poverty, its injustice, and its alienated underclass
2 . the weakest part of an organization or a person’s character, that is most easily attacked or criticized
underbelly of
They needed to find the soft underbelly of their opponents.
3 . the lower part of an animal’s body, including the stomach