The adjective for Barbados is arbarian or Bajan
West Indian or Antillean is the proper adjective for West Indies.
Barbadian can be a noun and an adjective. Noun: Someone from Barbados. Adjective: Of, or relating to, Barbados.
The proper adjective for southwest is "southwestern."
The proper adjective is Haitian.
The proper adjective for Portuguese is "Portuguese."
Vietnamese is the proper adjective for Vietnam.
The proper adjective for Georgia is Georgian.
The proper adjective for George is Georgian.
Freudian is the proper adjective for Freud.
Mayan is itself a proper adjective.
The proper adjective for Siam is Siamese.