Log in to your server as root and find the process PID your want to kill. You can do that by using ps command with aux options :
ps aux
This will display all process lists. For example:
root 373 0.0 0.1 8124 7604 ? Ss 01:56 0:00 somecommand
Second number is the PID. You can kill the process using this PID using command below:
kill 373
