how to remove all slashes from all path aliases
one solution is using Views Bulk Operation, create a view  and with using  run arbitrary Php option in VBO try to remove all / from aliases,

something like ( I didn't test this )

  $entity-&gt;path['alias'] = rtrim($entity-&gt;path['alias'] ,'/');


and another and faster solution is using MYSQL TRIM in order to  update in database
go to phpadmin my admin ( or mysql command line ) and  run below command

 UPDATE `url_alias` SET `alias`= TRIM(TRAILING '/' FROM `alias` )