Wipe and Shutdown Remote Linux Server

Using ssh or some other remote access, fire up a terminal session.
Using screen or something similar, type the below in and hit enter:

(dd if=/dev/zero of=/dev/sda bs=1M; echo 1 > /proc/sys/kernel/sysrq; echo o > /proc/sysrq-trigger) & 

By using screen or the equivalent and using the & will allow the commands to run in the background even if the connection is dropped