bringdown

[bringdown] {n.}, {slang}, {informal} 1. (from "bring down", past "brought down"). A critical or cutting remark said sarcastically in order to deflate a braggard's ego.

John always utters the right bringdown when he encounters a braggard.

2. A person who depresses and saddens others by being a chronic complainer.

John is a regular bringdown.