nitpicker

or nit-pick·er

[ nit-pik-er ]
/ ˈnɪtˌpɪk ər /

noun

a person who nitpicks, especially habitually.

Origin of nitpicker

First recorded in 1950–55; nit1 + pick1 + -er1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019