Heidi Turner was more evil than Cartman in that plotline, and although Cartman does absolutely “chaotic evil” things, he also considers himself patriotic and thinks cops are cool.

That might make him more Neutral Evil or Lawful Evil despite cooking Scott Tenerman’s parents.

But I think Heidi is the chaotic evil because Mr. Mackey says “She’s like Cartman but worse because she’ll actually follow through.”