Oedipus Rex is considered the best example of a complex tragedy by Aristotle in his Poetics.
To begin with, a tragedy goes from good to bad or bad to worse. In the beginning of the play, the people of Thebes are dying a plague. In an effort to to find the cause, Oedipus has sent his brother in law to the oracle to find out the reason.
He is told that the plague will be lifted once the murderer of the former king, Laius, has been found and punished. Being a good king, Oedipus promises to do everything in his power to find out who killed Laius.
He questions various people including the soothsayer, Teiresias, and several others in a effort to discover the answer. A messenger from Corinth arrives to tell him that his parents, the king and queen of Corinth have died.
Oedipus is relieved since it was prophesied by the Oracle of Delphi that he would kill his father and marry his mother and since he had been in Thebes when his father died, this must have been a false prophesy.
It is at this point that it is revealed that he was not their natural son. He had been adopted by them when he was a baby.
This king, this husband, this father, discovers that he doesn't know who he is.
From this point the play becomes like a boulder rolling down hill. The truth becomes unstoppable as the pieces of the puzzle begin to take shape.
Like all men, Oedipus is flawed and in this case his flaw is too much pride, which he seemed to have inherited from his father, Laius. Pride would not permit either man to give way on the narrow mountain road and as a result while trying to escape his fate, Oedipus walked right into it.
Is Oedipus a bad man? No, in fact he is a good king. Does he deserve his fate? I don't think so. He is a victim from birth.
Catharsis, one of the important features of tragedy, is defined as a cleansing through the emotions of fear and pity. We fear because Oedipus, a good man, is cruelly punished for something done by his ancestors. If this is true, what about the rest of us? We also pity him because he tried to avoid his fate which was something anyone would try to avoid and suffers as a result.
The play began with a plague and a mystery and by the end Oedipus was blind and an outcast, Jocasta was dead, and and his four children discovered that they were also his half brothers and sisters. The plague was lifted but Thebes would never be the same. Things definitely went from bad to worse.
You have asked two questions, but I am allowed to answer only one at a time. You must list the second question as a separate posting.
The tragedy of Oedipus is a famous one.
At the start of the play, a Priest and people of Thebes come to Oedipus to ask for help, which he promises. They tell him they have been hounded by terrible disasters because someone in Thebes killed King Laius. Oedipus promises to find out what is going on.
The history that leads to this point of the play is that Oedipus is the true son of Laius and Jocasta, King and Queen of Thebes. One day an oracle (fortune teller) declares that Oedipus will kill his father and marry his mother. To prevent the prophecy from coming true, the parents decide the child must die. A servant takes their baby to kill him, but decides instead to abandon him on a mountain side, expecting he will starve to death.
After the servant leaves, however, a shepherd finds the child and takes him to another country to avoid his fate. Ultimately, the child finds his way into the household of King Polybus of Corinth, who raises Oedipus as his own. Oedipus knows nothing of this. One day he is attacked by a two men on the road; unknowingly, he kills his father, as he slays both men.
Oedipus becomes King of Thebes because he solves the riddle of the Sphinx, a monster who was eating all passersby if they could not answer his question. To further honor him, the people of Thebes insist Oedipus marry Jocasta. No one knows that he is marrying his mother. They have children.
After Oedipus promises to find the murderer of the former king, he speaks to an oracle who tries to tell him that HE is the murderer he seeks. Oedipus does not believe this. He feels that it is a plot by Laius' brother (Creon) to steal the throne from him. Creon swears this is not true. To intercede for Creon, Jocasta repeats the story of her husband's death as a witness had reported it to her.
Hearing the details, Oedipus realizes that he did, in fact, kill Lauis, but believes that Polybus was his true father, a man who died of old age; Oedipus therefore believes he did not kill his father.
In the meantime, the shepherd who had left Oedipus on the mountain side comes to Oedipus and reports that he was, in fact, the child of Laius and Jocasta. Jocasta kills herself realizing she has married and born children to her son. Devastated by the truth, Oedipus puts out his eyes, though this does not put his mind at ease. He asks Creon to care for his daughter; Oedipus says his farewells to his daughters. Then he asks Creon to exile him from the city. And so the play ends.
In summary, the tragedies are that Oedipus unknowingly kills his father and marries his mother (and they have children), his mother/wife kills herself, and he blinds himself and leaves Thebes.