I still think that is just Najenda's opinion. I don't think that Esdeath is any more evil than, say, Ares or Achilles from Greek Mythology. She just really likes war, common for people living in older more barbarous times.
In fact, I read the chapter as confirming that Esdeath is not evil. She withheld that last power until she had no more allies in the capital and ensured that it would not affect her subordinates, i.e. she was protecting them, even if she still doesn't care that much for them.