Magento Remove all Customers with Reset Id

Run Below Query in your database.please make a backup your db

SET FOREIGN_KEY_CHECKS=0;
-- reset customers
TRUNCATE customer_address_entity;
TRUNCATE customer_address_entity_datetime;
TRUNCATE customer_address_entity_decimal;
TRUNCATE customer_address_entity_int;
TRUNCATE customer_address_entity_text;
TRUNCATE customer_address_entity_varchar;
TRUNCATE customer_entity;
TRUNCATE customer_entity_datetime;
TRUNCATE customer_entity_decimal;
TRUNCATE customer_entity_int;
TRUNCATE customer_entity_text;
TRUNCATE customer_entity_varchar;
TRUNCATE log_customer;
TRUNCATE log_visitor;
TRUNCATE log_visitor_info;

ALTER TABLE customer_address_entity AUTO_INCREMENT=1;
ALTER TABLE customer_address_entity_datetime AUTO_INCREMENT=1;
ALTER TABLE customer_address_entity_decimal AUTO_INCREMENT=1;
ALTER TABLE customer_address_entity_int AUTO_INCREMENT=1;
ALTER TABLE customer_address_entity_text AUTO_INCREMENT=1;
ALTER TABLE customer_address_entity_varchar AUTO_INCREMENT=1;
ALTER TABLE customer_entity AUTO_INCREMENT=1;
ALTER TABLE customer_entity_datetime AUTO_INCREMENT=1;
ALTER TABLE customer_entity_decimal AUTO_INCREMENT=1;
ALTER TABLE customer_entity_int AUTO_INCREMENT=1;
ALTER TABLE customer_entity_text AUTO_INCREMENT=1;
ALTER TABLE customer_entity_varchar AUTO_INCREMENT=1;
ALTER TABLE log_customer AUTO_INCREMENT=1;
ALTER TABLE log_visitor AUTO_INCREMENT=1;
ALTER TABLE log_visitor_info AUTO_INCREMENT=1;
SET FOREIGN_KEY_CHECKS=1;