Irony

Saying one thing while meaning another, often the opposite. The true meaning is left to whoever reads or hears.

In The Slum

a tal carta de liberdade era obra do próprio João Romão, e nem mesmo o selo, que ele entendeu de pespegar-lhe em cima, para dar à burla maior formalidade, representava despesa porque o esperto aproveitara uma estampilha já servida, that so-called letter of freedom was the work of João Romão himself, and not even the stamp, which he took it into his head to slap on top of it to give the sham greater formality, was an expense, because the sly one had reused a stamp already used

The narrator calls the forger "sly" and speaks of a "greater formality" for a sham: the apparent praise exposes the character's fraud and meanness.

Chapters I to II: João Romão's Tenement and Miranda's House, the narrator

lançava para baixo olhares de desprezo sobre aquela gentalha sensual, que o enriquecera, e que continuava a mourejar estupidamente, de sol a sol, sem outro ideal senão comer, dormir e procriar, he cast looks of contempt down on that sensual rabble, which had enriched him and which went on toiling stupidly from sunup to sundown, with no ideal other than eating, sleeping, and breeding

Chapters XII to XIV: Marriage, the Rival Tenement, and the Plan of Revenge, the narrator

Seria um ato de justiça!, It would have been an act of justice!

Chapters XVIII to XX: Libório, the Renovations, and Piedade's Fall, João Romão

O cortiço aristocratizava-se, The tenement was becoming aristocratic

Chapters XXI to XXIII: Bertoleza's End and Romão's Rise, the narrator