Whatever we do if we catch them, we cannot make them martyrs in life or in death. And we must ignore, dehumanize, and marginalize them in their deaths as much as possible in the media-- no articles about who they were, etc. The only thing media should call them is murderer or terrorist--no names. Quick cremation or anonymous and hurried burial, after we forensically process the corpses of the terrorists. No ceremonies or dignity. They do not deserve the dignity they denied to their victims, even in death, IMO. Once dead, IMO they are just a carcass we need to dispose of.
There is no "saving" the terrorists. If we catch them alive, we should get all the info out of them we can, and then they should never be allowed out of max security prison again. And really there is no way to punish them adequately, short of torture or humiliation-- which most civilized people find abhorrent, even for terrorists. Once radicalized, they are sub-human and lost forever, IMO. We just need to store them away cheaply and anonymously for some years till they die. I'm just fine with a lifetime of solitary confinement and a boring and minimal diet for these animals. Or a swift death penalty-- I'm fine with that, too.
Isabelle is right-- there is no "punishment" for them-- so I think we just need to figure out what works for us cheaply and securely, to manage and store their sorry hides till they die.