Hang them with cheap rope and a garbage sack tied around the waist to catch the drippings and toss them into the nearest dumpster.
Nevertheless, I think some very stark vivid object lesson sorts of executions do need to take place for the worst of them. It's not a fun thing to contemplate, per se.
Yet, I understand they have loved ones, families--some of whom may be relatively innocent. I have no need to embitter them by some kind of off the wall cruelty in executing their loved one. But I still think a very stark and vivid message needs to be sent via their manner of execution.
What about the meat hooks? Remember Italy, 1945?