An example of child abuse in The Adventures of Huckleberry Finn is Huck’s father abandoning his son, and physically abusing him when he is around.
Huck Finn’s father is without a doubt one of the vilest characters in the book. He is a drunkard who only cares about his son when he thinks he can get some money from him. As a result, Huck is mostly homeless and lives under the radar.
Life with Pap was terrible for Huck. His father’s physical abuse was pervasive.
He used to always whale me when he was sober and could get his hands on me; though I used to take to the woods most of the time when he was around. (ch 3, p. 12)
Huck manages to live with the Widow Douglass, partly because Tom Sawyer convinces him. Everything is better, except that Huck has to be civilized, until he finds a footprint with a cross in the heel and he knows it is his father. Huck consults the hairball, but before he knows it his father is sitting on his own bed.
Normally you would think a father would be thrilled to know that his son was well taken care of, and was getting an education and going to church. Pap has the opposite reaction.
You've put on considerable many frills since I been away. I'll take you down a peg before I get done with you. You're educated, too, they say—can read and write. You think you're better'n your father, now, don't you, because he can't? (ch 5, p. 17)
Pap’s concern with Huck’s “meddle with such hifalut'n foolishness” is not his main purpose for coming. He has heard that his son has a fortune, a result of the treasure he and Tom found from the gang of robbers. He insists that Huck give it to him and is angry when he can’t.
Huck's father's abuse serves as an explanation of why Huck lives by himself and is not comfortable with the trappings of civilization. He has been raised, if you can call it raising, in a perpetual state of turmoil. As is often the case, meeting the father helps us better understand the son.
Although Pap’s presence in the novel is highly comical when he is not beating Huck, he serves a more significant literary purpose—he is Huck’s impetus to leave. Huck’s father is so abusive that he cannot stay, and so he fakes his own death and takes off down the river.
The main example of child abuse in this novel is that suffered by Huck himself, at the hands of his father. His father is an iredeemable drunk, poor and full of resentment at society which he feels has completely let him down. He takes out his frustrations on Huck. When he returns at the beginning of the book, to find Huck has been adopted by the Widow Douglas, he vows to get Huck back from what he sees as interfering do-gooders. Huck doesn't actually might leaving the stifling attentions of the widow Douglas and her sister Miss Watson, but his father takes to regularly beating him and locking him in the shack where they live, and finally attacks him with a knife in a drunken fit, so that at last he determines to escape. This is the starting point of his adventures down river with Jim, which form the main portion of the book. It is the treatment by his own father which becomes the immediate cause of his departure from society.
Huck's abuse by his father is quite a shocking aspect of the story, although it doesn't actually take up much of the narrative, and Huck himself never really comments on it and relates it quite matter-of-factly.