Hoarder, who has a condition as described by wikipedia:
Compulsive hoarding, also known as hoarding disorder, is a pattern of behavior that is characterized by excessive acquisition and an inability or unwillingness to discard large quantities of objects that cover the living areas of the home and cause significant distress or impairment.
What would you call the opposite of a hoarder, a person who tries to have as few possessions as possible, sometimes taking it too far? To fit sentences similar to this:
Michael's behavior as a _____ often causes difficulties. An example: he divests of common use tools when done with a project–then when a similar project occurs in the future, he has to spend time and money to reacquire tools that he should have kept in the first place.
Best I've come up with is minimalist. But many readers will have a positive connotation of that.
Best Answer
One article describes it as a mental illness: obsessive-compulsive spartanism. That's fairly negative, but you might not want the added baggage of diagnosing someone with a mental illness, so just spartanism might be a good alternative. Spartanism is a little more neutral to me than negative, but some folks might see it as slightly negative.
An article in the Atlantic - The Opposite of Hoarding discusses the challenges faced by folks with this specific flavor of compulsive disorder, because of the cultural view of 'decluttering' as a positive thing. It says "...there’s no official term for compulsive decluttering."