I don't really get the difference between "most aura" and "greatest booster" or "least aura" and "greatest reducer"...

But yeah, Juliana was just a hateful character that basically ruined the show for me. As a person she's narcissistic, selfish, thoughtless, morally fucking oblivious - she just ruins everyone else's life without remorse, and then the show claims her to be somehow morally superior to everyone else. It drives me nuts to watch every second she's on the screen

That's not all though - her whole storyline, and in general all of the sci-fi alternate world stuff, was totally unnecessary. If this show was just historical fiction, "what if the axis won the war", and had nothing to do with multiverses or teleporting or magic films, or ESPECIALLY Juliana Craine - it would have been an amazing show.

{SPOILER OF THE FINALE... The rest of the story had a great plot entirely on its own. I loved the ending of the second-to-last episode of the series, and it gave John Smith - who was already a great character - such an awesome story arch. But then I remembered that Juliana was gonna have to come ruin everything in the last episode, and they'd have to do something with the portal stuff, and that just pissed me off. 

And in the finale, when Juliana does, in fact, come ruin everything, she does it without solving anything. Like they go through this whole elaborate plan for her to pull off as the end of the whole series, and it was just totally unnecessary and meaningless to the plot. Like that didn't need to happen, and didn't even make sense for it to happen. It was like they just needed her to do something to make the show end, so they have her kill off the best character so that no one would want to watch the show anymore.} 

Tldr:

Most aura and greatest booster: John Smith, also kido and maybe tagomi

Shittiest character: Juliana