If you describe something bad that happens to someone as poetic justice, you mean that it is exactly what they deserve because of the things that person has done.

For example:

After spending his career manipulating others, it was poetic justice that his own investments led to his financial ruin.

The bully who loved to trip people ended up tripping on a loose rug himself; it was pure poetic justice.

The character who always cheated in games finally lost due to a technicality he himself had exploited in the past, a perfect example of poetic justice.

In a surprising turn of events, the greedy landlord who evicted his tenants was himself evicted from his own property due to a technicality in the building code. What poetic justice!

It was poetic justice that the con artist who swindled people out of their savings was then scammed out of his own fortune by an online scheme.

Tradução:

Em português, “poetic justice” significa justiça poética. Refere-se a uma situação em que algo ruim acontece a uma pessoa que parece merecer isso, especialmente devido a ações más que ela tenha cometido. É uma forma de recompensa ou punição que parece ser apropriada e justa, como se fosse resultado de um plano bem elaborado ou de um desfecho ideal de uma história. 

A justiça poética pode ser vista em muitas obras de arte, como filmes, livros, peças de teatro e até mesmo na vida real, quando situações se desenrolam de uma forma que parece ser uma recompensa ou punição adequada.