Final answer:
A protagonist who suffers a rise in fortune followed by a sudden downfall is known as a Tragic Hero, an archetype defined by Aristotle that also experiences peripeteia and anagnorisis leading to a cathartic effect.
Step-by-step explanation:
The character archetype you're referring to is known as a Tragic Hero. According to Aristotle Poetics a tragic hero starts off in a high position and is generally virtuous but possesses a flaw, or hamartia, which leads to their fall from grace a downfall that includes a reversal of fortune known as peripeteia. This character experiences a moment of realization or anagnorisis, understanding their fault and the inevitable consequences of their actions. Oedipus from Sophocles' play is a classic example of a tragic hero, whose downfall is the result of his pride and leads to a cathartic experience for the audience.