Langston Hughes' poem "The Ballad of the Landlord" contains not only one figure of speech, but rather many. Figures of speech are generally used by a poet to give particular stylistic effect. Most of the figures -- or rhetorical devices -- in this poem function to communicate the mounting frustration of the tenant/poet-speaker as he is faced with the futility of his complaints.
Hyperbole or exaggeration is used to convey the desired effect of the poem: to indicate the tenant's anger and the landlord's unwillingness to make the necessary repairs to the apartment. The tenant, in order to be heard, feels that he must exaggerate, that is, use hyperbole. Lines 21-24 read, "Police! Police! / Come and get this man! / He's trying to ruin the government / And overturn the land!" The tenant's threat to call the police appears to be hyperbolic at first -- that is, you might think that he never actually intends to call the police -- but, as you find out later in the poem, he really does call them. However, the statement that the tenant makes to the police about the landlord trying to "ruin the government" is hyperbolic: The landlord is only refusing to make repairs on the apartment.
This is a device that substitutes an inoffensive -- or in this case, less aggressive -- statement for the unpleasant meaning that the statement actually conveys. For example, "You ain't gonna be able to say a word / If I land my fist on you" is meant to tell us that the tenant is threatening to break the landlord's jaw, not merely to prevent him from talking.
A rhetorical question is one to which the speaker and listener already know the answer. These kinds of questions are used in place of a statement to give greater expressive and persuasive force: "Ten Bucks you say I owe you? / Ten Bucks you say is due?" The tenant has obviously heard the landlord and already knows the price of rent. These questions are much more forceful than statements. For example, "I owe you ten bucks. You said ten bucks is due" just doesn't pack the same expressive punch. Another example: "What? You gonna get eviction orders? / You gonna cut off my heat? / You gonna take my furniture and / Throw it in the street?" Again, the tenant seems to be repeating the landlord's statements in the form of rhetorical questions. This could be the tenant making an effort to emphasize the unfairness of these actions. Whether or not the landlord is sympathetic, we can only guess.
Overall, "The Ballad of the Landlord" is leading up to a climactic use of irony. Typically, irony refers to the use of words to convey the opposite of their literal meaning. However, here, thematic irony is used, in which several episodes lead up to an unexpected outcome: The tenant calls the police to report that his landlord is -- illegally -- refusing to make basic repairs on his apartment. However, the police arrest the tenant instead. To understand this irony, it helps to look at the historical context. Hughes bases this poem on actual living conditions in 1930s Harlem, a time and place in which African-Americans were discriminated against based solely on race.