Using Fcremove.exe is relatively straightforward. Here are the steps:
cd /d "C:\Program Files (x86)\Fortinet\FortiClient" forticlient fcremove.exe
There are several reasons why you might need to use Forticlient Fcremove.exe: Using Fcremove
On rare occasions (particularly with FortiClient 5.x or 6.x), fcremove.exe may leave behind registry keys that block future installations. Perform this manual sweep: forticlient fcremove.exe