Guachi
Guachi was a language isolate once spoken in Brazil.
An isolate: no relationship to any other known language has been demonstrated.
Guachí (Wachí) is an extinct language isolate, possibly related to Guaicuruan, of Brazil. It is usually classified as one of the Guaicuruan languages, but the data is insufficient to demonstrate that. The people it was spoken by were Guaicuruanized.
From Wikipedia · Guachi language · CC BY-SA 4.0