There is no API to get all user profile in a single request. You need some filter and paging to get user profiles.
Using Search API
In first request, above API will return you 100 profiles who have first name started with
A. In second request
startrow will be
100. This way you can get your all user profiles.
You can get all user profiles under your current logged in site from below end-point. Make a GET request to the following URL.
In next requests increment the value of
(previous + 100).