Replace the prefix in wp_users
and wp_usermeta
table names for the one you use.
Make backup of data from both tables before you start to delete users.
DELETE u FROM wp_users u
LEFT JOIN wp_usermeta um1 ON u.id = um1.user_id AND um1.meta_key = 'first_name'
LEFT JOIN wp_usermeta um2 ON u.id = um2.user_id AND um2.meta_key = 'last_name'
WHERE (um1.meta_value IS NULL OR CHAR_LENGTH(um1.meta_value) = 0)
AND (um2.meta_value IS NULL OR CHAR_LENGTH(um2.meta_value) = 0);
DELETE um FROM wp_usermeta um
LEFT JOIN wp_users u ON u.id = um.user_id
WHERE u.id IS NULL;