A person, usually a fanboy type, who desires to collect all the work of a specific author or artist. Most common with jazz and rock musicians, where studio outtakes and live performances are collected and traded. Generally mildly derogatory.
You'd think he'd give it up after the fourth Dick's Picks CD, but truth be told he's just an over-the-top Dead completist.
A person who obsessively attempts to collect an example of every item in a particular field.
A video game player who will play each level until all possible collections, statistics, and quests are completed.
My boyfriend played one level of SO4 for five hours trying to get every last monster; what a completist!