Not sure about that as everybody has their limit, their own breaking point, a point at which they can take no more etc. I for one just like Harry would definitely want to see this man suffer for the pain he has inflicted on others.
Any type of imprisonment imo is not enough for someone like him and really the only punishment justified enough for his crimes against humanity is a slow agonising death.
Personally though I think it should be left to the families of his victims to decide a punishment or execution style for him but that will never happen as it will surely breach some BS human rights bill from the EU bureacrats.