When Agustin-Iturbide abdicated his power, he d. gave it up voluntarily.
Why did Agustin-Iturbide abdicate his power voluntarily?
On March 19, 1823, Agustin-Iturbide stepped down, after facing increasing opposition and instability in his reign as Emperor of Mexico.
He recognized the wishes of the country and the support for the Plan of Casa Mata, which called for a republic.
He agreed to stand down to avoid a violent civil war and to make sure there was a peaceful transition of power.
Hence, while it's true that he faced opposition and pressure, his abdication was definitely a voluntary decision.