Sometimes you might not be able to remove iotedge for whatever reason. This can happen if you have installed it long time ago and new scipts (usually powershel scripts like this one 'aka.ms/iotedge-win')
As first you have to remove the service by using following command:
sc.exe delete "iotedge"
Then remove environment variable with following command or manually:
Remove-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager\Environment' -Name 'IOTEDGE_HOST'
Finally, remove the folder with iotesge service.
Note, there is also a folder with log file. Usually stored on this location: 'C:\ProgramData\iotedge-eventlog'
I cannot guarantee, that this will clean-up all required resources. But it helped me a lot.
Please not that this is NOT AN OFFICIALL WAY to remove the runtime.