malesperi

This is esperi with mal- bolted on the front, and the word is worth learning precisely because it shows how far that prefix reaches: hope becomes its exact opposite with two letters and no new root. The same stem gives you malespero for despair the noun, malespera for the adjective, and malesperiga for something that drives you to it. Note that it is intransitive and takes pri for the thing despaired of, so mi malesperas pri li, never a bare accusative. The imperative ne malesperu is common in Esperanto's older literature, which was written by people with plenty to despair about.