If you're new to the series, there are a few streaming options that'll allow you to watch Avatar: The Last Airbender - especially if you're curious to see what happens next after the season one ...
Sozin's Comet, Part 4 - Avatar Aang: In the climactic series finale, Aang finally faces the firelord. (S3, ep 21) We’re sorry, the information you’re looking for ...