How to kill terminal server sessions

There are two quite useful line commands to do so. 

qwinsta and rwinsta

qwinsta: queries for sessions

rwinsta: remove sessions.

To display command options use qwinsta /? and rwinsta /?

here is a list of these command's options

qwinsta /? 

Display information about Terminal Sessions. 

QUERY SESSION [sessionname | username | sessionid] 
              [/SERVER:servername] [/MODE] [/FLOW] [/CONNECT] [/COUNTER] 

  sessionname         Identifies the session named sessionname. 
  username            Identifies the session with user username. 
  sessionid           Identifies the session with ID sessionid. 
  /SERVER:servername  The server to be queried (default is current). 
  /MODE               Display current line settings. 
  /FLOW               Display current flow control settings. 
  /CONNECT            Display current connect settings. 
  /COUNTER            Display current Terminal Services counters information. 

rwinsta /? 
Reset the session subsytem hardware and software to known initial values. 

RESET SESSION {sessionname | sessionid} [/SERVER:servername] [/V] 

  sessionname         Identifies the session with name sessionname. 
  sessionid           Identifies the session with ID sessionid. 
  /SERVER:servername  The server containing the session (default is current). 
  /V                  Display additional information. 

Regards!