KILL (Resource kit)

Remove a running process from memory.

Syntax
      KILL [option] process_id
      KILL [option] task_name
      KILL [option] window_title

Option
        -f     Force process kill

Kill -f basically just nukes the process from existence, potentially leaking a lot of memory and losing any data that the process hadn't committed to disk yet. It is there for worst case scenarios - when you absolutely must end the process now, and don’t care whether proper cleanup gets done or not.

In Windows XP, KILL is replaced with the superior TASKKILL - Allowing you to specify a remote computer, different user account etc - for more details run TASKKILL /?

“If you're going to tell people the truth, you'd better make them laugh, Otherwise they'll kill you” - George Bernard Shaw

Related:

PsKill - Kill processes by name or process ID
PsSuspend - Suspend a processes
TSKILL - Kill process on a Terminal Server
TASKKILL - Kill a local or remote task (XP)
PsList List detailed information about processes
NET - Stop a service from running
NET FILE - Force an open file to close
RKILL - Remote Kill (Resource Kit) view or kill processes on a remote server
Powershell: Stop-Process - Stop a running process (kill)
Q171773 - Kill a background process
Q178893 - Terminate an Application "Cleanly" in Win32
Q197155 - How to Kill an Orphaned Process
Equivalent bash command (Linux): kill - Kill a process