Aristotle, in his "Poetics" identifies two kinds of drama and poetry, from which all other models are derived. This remains true today!
The two kinds of drama are (1) Comedy; and (2) Tragedy.
The comedy arc begins happy, has a crisis, then resolves happily again (think of most comedies and romances you've seen or read):
The tragic arc is the opposite; the drama begins in some crisis, then appears to improve, but then collapses in the end: tragic!
Can you think of any poetic or dramatic examples (books, movies, etc) of the tragic arc? Share them here!