The below script will drop all the objects owned by a schema. This will not delete the user but only deletes the objects

SET SERVEROUTPUT ON SIZE 1000000
set verify off
BEGIN
FOR c1 IN (SELECT OWNER,table_name, constraint_name FROM dba_constraints WHERE constraint_type = 'R' and owner=upper('&shema_name')) LOOP
EXECUTE IMMEDIATE 'ALTER TABLE '||' "'||c1.owner||'"."'||c1.table_name||'" DROP CONSTRAINT ' || c1.constraint_name;
END LOOP;
FOR c1 IN (SELECT owner,object_name,object_type FROM dba_objects where owner=upper('&shema_name')) LOOP
BEGIN
IF c1.object_type = 'TYPE' THEN
EXECUTE IMMEDIATE 'DROP '||c1.object_type||' "'||c1.owner||'"."'||c1.object_name||'" FORCE';
END IF;
IF c1.object_type != 'DATABASE LINK' THEN
EXECUTE IMMEDIATE 'DROP '||c1.object_type||' "'||c1.owner||'"."'||c1.object_name||'"';
END IF;
EXCEPTION
WHEN OTHERS THEN
NULL;
END;
END LOOP;
EXECUTE IMMEDIATE('purge dba_recyclebin');
END;
/