Before i share my ideas, you want a solution that makes Dawn more sympathetic, or something that makes her a more definite villain?

Not a problem dude! You can as you want! I did wish she was written better as a villain or role of the main antagonist of the movie, or witha second option a different character or someone we don't know (like one of the characters in the movie I do think would work better than Dawn which is what I will do later whenever I feel want to do it).

You can tell me.

Maybe revealing her twist a bit early than the climax. This is the same problem I had with Turbo.

A. The sympathetic solution: Dawn was the literal black sheep of her family, and her racist family hated her because she reminds them of a black panther, so they threw her out of the house. She let the insults of how she reminds a black panther to get into her head, and decided to blame the carnivores as a whole in her situation, because she couldn't bring herself to blame her parents. Thus, she came up with the canon scheme and revealed herself as the villain at the end of the second arc when she tried to convince Judy to join her ("when you're accused at looking like a black panther, eventually you start to act like one. Stick with me and no one will mock you ever again").

B. The hate sink solution: Dawn is an obvious villain to the audience (it fixes the twist decay of a twist villain whose twist was poorly-handled), and Judy suspects her too, but she suffocates her suspecions with a pillow because she really needs to trust someone. Also, she's not a sheep in this solution. She's a pig who encourages Mayor Lionheart to become more and more corrupted.

Have her be evil from the start and show how she manipulates Judy from the shadows.

For me like ScaryMovie53! But have the twist reviled a bit eelier in the climax! Though I do wonder if she'll make a second appearance in the sequel movie will she be better written there?

Perhaps, but i do think and always predict and wish new Zootopia main antagonist for the sequel like a red Boa Constructer with a scar and can be a Palpatine or Hopper for the intelligence, Rattlesnake Jake for his skills, and be like a seiral killer like not William Afton, instead based on Freddy Kreuger or Scarecrow but in Disney way (but in a god way, not the predictable "ohh too scary for kids" bullcrap).