Who or what is the antagonist and what is he or she like in The Hobbit?

Answer 1

There are a number of them. If you cite Biblo as the primary protagonist, and the dwarves as secondary, then the primary antagonist is Smaug, which the lessers being the Tolls, the Goblins of the Misty Mountains, Gollum (only for Bilbo), the Spiders of Mirkwood, Mirkwood itself, the Elves of the Woodland Realm, and the Men of Esgaroth on the Long Lake. At some point, all of them stood opposed to the Dwarves and Bilbo on their quest.

Each of them is very different in their motivations too.

The Trolls: Mostly motivated by hunger, which made them difficult to deal with for Bilbo. They were dim-witted, though, which was how Gandalf was able to trick them.

The Goblins: The goblins were belligerent and confrontational, but that's their nature. Things might have gone differently had they not seen the Elf weapons and Gandalf not killed The Great Goblin. In the later parts of the book, they are motivated by revenge.

Gollum: In The Hobbit, Gollum is motivated by hunger and his love of the Ring. AS a result, he was a conniving and deceitful. He planned to kill Bilbo no matter who won the contest of riddles. After losing the ring, he becomes unstable and more violent.

Mirkwood: the forest is presented as almost being alive it its own right. It was dark, foreboding and didn't seem to want to let the Dwarves escape.

The SPiders: the spiders, also motivated by hunger, were primarily used as a means to establish Bilbo as a capable member of the party. They were aggressive and evil.

The Elves: The Elves just wanted to be left alone. They saw the Dwarves intrusion as an attack - or begging. When the Dwarves fled Erebor, they were well known to be beggars. Very few trusted them, and no one less than Elves.

The Men: The men saw the Dwarves return as an good omen, since most of them were descendants of the lost town of Dale. They assumed the Dwarves knew how to get rid of the dragon. After the Dragon was slain, they felt that the Dwarves should compensate them, but the Dwarves were too greedy.