Who is the controversial character in Huckleberry Finn?

I'm curious, who exactly is the character that sparks the most debate and controversy in Mark Twain's classic novel, Huckleberry Finn? Is it Huck himself, for his adventurous spirit and moral dilemmas, or is it someone else entirely? I'm eager to hear your thoughts on the matter and how this character's presence shapes the narrative and the broader themes of the story.