IPA: /kəmˈpliːtɪst/
KK: /kəmˈplɛtɪst/
A person who tries to collect or complete everything related to a particular subject or category.
As a completist, she aimed to own every edition of her favorite book series.
A person who tries to collect or obtain every item in a specific category or collection.
As a completist, she aims to own every album by her favorite band.
Completist → It is formed from "comple" (from Latin "completere", meaning to fill up or finish) and "-ist" (meaning a person who practices or is concerned with something). A completist is a person who seeks to complete or finish everything in a particular category or collection.
Think of someone who wants to 'finish' ('comple') everything in their collection — that's what a completist does.