To quote Donald Pleasance from Halloween: "I spent eight years trying to reach him, and then another seven trying to keep him locked up because I realized that what was living behind that boy's eyes was purely and simply... evil."
Homolka is arguably worse than Bernardo. Both are psychopaths, but Homolka is so far gone that even the female inmate she slept with in prison found her to be more than a little scary sometimes.
As for the head-shrinker’s take on Karla... (from wikipedia)
http://en.wikipedia.org/wiki/Karla_Homolka#Prison
“a certain moral vacuity” is a bit of an understatement.
To quote Donald Pleasance from Halloween: "I spent eight years trying to reach him, and then another seven trying to keep him locked up because I realized that what was living behind that boy's eyes was purely and simply... evil."