arminmeth

While WordPress is slowly but surely becoming a complete application framework and JSON REST API is huge step in this direction, there is a large number of WordPress users that do not need advanced features like those offered by WordPress JSON REST API. This plugin helps them to turn those advanced features off and not worry about it.
While other similar plugins disable JSON REST API functionality only for anonymous users, Kill JSON REST API completely disables the framework for all users and removes links and tags from head element.

Kill JSON REST API

Completely disables JSON REST API for both registered and anonymous users in WordPress 4.7.* and removes API links and tags.

Rajat

This Plugin Create a options which can provide ability to disable all or particular routes for json api.This plugin 
help to restrict the use of public credentials of website.This will protect the data such as users details of wordpress 
etc

Restrict Json Rest Api

Plugin to restrict json rest api, which you want to restrict to use from outside

Kill JSON REST API vs Restrict Json Rest Api