mysql privilege to kill processes of other users
From here


  If you have the PROCESS privilege, you can see all threads. If you
  have the SUPER privilege, you can kill all threads and statements.
  Otherwise, you can see and kill only your own threads and statements.
  
  You can also use the mysqladmin processlist and mysqladmin kill
  commands to examine and kill threads.


See here for privilege granting - search for SUPER.