I'm just so curious about what he lost... did he lose inflexibility? But he was flexible before.. did he lose his jadedness?
Clearly he has changed, his mentality is definitely not that of a several hundred year old man who watched everyone die and lived long enough to be forgotten... he's basically rediscovering humanity. I just keep thinking the void, that 10% he lost was his anger/lack of passion, the part that drove him to be a 'Demon Lord'.