Final answer:
The missing word in the sentence is 'falta' which means 'lack' or 'miss'in Spanish.
Step-by-step explanation:
The missing word that best completes the sentence is ' falta'. The original sentence can be translated as 'I don't lack anything. I have everything.' In this context, 'falta' means 'lack' or 'miss'.
Learn more about Spanish words and their meanings