Suppose Isser Harel had successfully nabbed Josef Mengele along with Adolf Eichmann, and so the "Angel of Death" was also put on trial (whether they'd be tried separately or together, I'm not sure). There's no doubt in my mind that Mengele would also be found guilty and executed. But what kind of impact would a "Mengele Trial" in 1961 have?
 
Mengele and Eichmann would be tried separately. In some ways Mengele's trial would be even more horrific, given what he personally did especially to children. Eichmann was a grey bureaucrat simply doing a job efficiently (at least in his own mind). Mengele, on the other hand, was a fiend who with his own hands performed acts of horror on children. In the case of Eichmann, while the "following orders" defense is indefensible, he could legitimately say he was placed in charge of a program and endeavored to run it as efficiently as possible. See Hannah Ahrendt's "Eichmann in Jerusalem" and her discussion of the banality of evil. OTOH Mengele actively sought out his role, personally selected his victims (particularly twins), and either directly or by direct order caused unspeakable things to happen. He devised the "experimental protocols" which treated human beings as lab rats in the worst ways.
 
I think that a trial (and likely execution) of Mengele would put something of a damper on Neo-Nazi movements down the line. Public tolerance of the incredibly broken people who make up the hard-core of those movements is going to be severely diminished when the most public face of Nazi-ism is a fully paid up hands-on monster with documentary and photographic evidence to prove it.
 
For an insight into Mengele close up, I'd recommend a read of Myklos Nizylli's "Auschwitz" - he was a Hungarian Jew, doctor, who was forced to help Mengele from August '44 onwards. It's a particularly chilling read.
 
Mengele and Eichmann would be tried separately. In some ways Mengele's trial would be even more horrific, given what he personally did especially to children. Eichmann was a grey bureaucrat simply doing a job efficiently (at least in his own mind). Mengele, on the other hand, was a fiend who with his own hands performed acts of horror on children. In the case of Eichmann, while the "following orders" defense is indefensible, he could legitimately say he was placed in charge of a program and endeavored to run it as efficiently as possible. See Hannah Ahrendt's "Eichmann in Jerusalem" and her discussion of the banality of evil. OTOH Mengele actively sought out his role, personally selected his victims (particularly twins), and either directly or by direct order caused unspeakable things to happen. He devised the "experimental protocols" which treated human beings as lab rats in the worst ways.

There are some people who'd probably disagree with you. Mengele would be easy to dismiss as a thoroughly sick and twisted individual, one that most people can be reasonably sure they'd never be like. Eichmann, however, was disturbingly normal. While Arendt may not have believed the idea that everyone has an Eichmann inside them, the fact that a seemingly ordinary man was responsible for organizing one of the most horrible crimes against humanity in all of history still raised a boatload of uncomfortable questions about human nature.

Not sure which side I fall on regarding who's more horrifying, TBH.
 
@Mort the Reaper : I take your point, lots of good literature about how ordinary Germans (and French, and Balts, and...) who were most definitely not psychopaths could drift in to accepting and performing acts of incredible horror. It would be so easy if the actions of the Holocaust, the GULAG, the Thai/Burma RR and so forth could be explained away as completely the act of clinically sick minds.
 
Top