Dirk’s apparent villainy could be seen as showing us that achieving the Ultimate Self is not always an objectively positive thing. Rose was a hero in both of her incarnations across the scratch, and the same could be said for basically all of the other kids save for perhaps Jake, who has all of John’s apathy and none of his drive.

But Bro is a version of Dirk who is explicitly a bad person. His intentions are benevolent to an extent, just as Dirk’s are; but the way he goes about them are undoubtedly evil, and Dirk himself seems to realise this. So by becoming his true self, Dirk is not just becoming the sum of all his good deeds; his the sum of all his bad deeds as well.

Jane, conversely, could be a good example of how reaching the Ultimate Self can save someone. John specifically cites Nanna as an adult version of Jane who was a good person, and not remotely evil! Nanna had first-hand experience with how bad the Condesce was, and was able to avoid becoming that kind of person herself. If Jane had been willing to absorb that part of her Ultimate Self, she may well have avoided straying down the path she did.