I think you mean Pius XI
Pius XII (twelfth) dropped the ball by not doing the consecration.
He also put Annibale Bugnini into office where he could destroy the liturgy.
He also revised Holy Week, the most ancient unchanged liturgy from the entire year.
He also did a number on the Psalms, which was unsuccessful so he had to re-do it a second time.
He also drastically revised the Breviary in a manner that many say was unnecessary.
No, I didn't mean Pius XI.