I really don't think he intented to cause the blackout, but stressed it since he wanted to revenge his son. You have to be awfully cruel to want to condemn the world to the horrors of a sudden blackout. Most supervillains probably would think it's a step to far.
I loved the kids playing with electricity-line, though.
One thought. If they destroy all these pendants, which seems possible if you know how to open them, is there a way to build new ones? Rachel has said that the key to turning on the lights has to do with them, and without them, the world should be screwed. If getting electricity back even is a good thing, I'm not really sure about that.