We don't have synonyms for completist yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are completion, completive and completing.
(n) :
(originally science fiction fandom slang) A collector who strives to obtain a complete collection of some type of thing, especially a fan who aims to own or consume the complete output of a particular author, publisher, musician or band.
(n) :
A person who champions any philosophy which focuses on the completeness of something.
(adj) :
Which attempts to collect something completely.
(adj) :
(obsolete) Alternative spelling of completest.
(n) :
(originally science fiction fandom slang) A collector who strives to obtain a complete collection of some type of thing, especially a fan who aims to own or consume the complete output of a particular author, publisher, musician or band.
(n) :
A person who champions any philosophy which focuses on the completeness of something.
(adj) :
Which attempts to collect something completely.
(adj) :
(obsolete) Alternative spelling of completest.