I'm learning Revolutionary Etude by Chopin (Op. 10, No. 12), and I am thinking about the last chord before the last four chords (fifth to the last chord, at the beginning of m. 81). Should it be fortissimo or not? It sounds awkward if it isn't, but the music technically shows that only the descending notes and onwards should be.
It must be quiet. It is the ending of the preceding phrase, and it should sound as though the piece has ended. The following ff descending line should be shocking. It's okay to make a ritardando as the phrase closes, which allows a little time between the chord and the descending line.
The Henle Urtext edition gives an explicit p on the chord in question. More importantly, they put the p mark there, because that is how it appears in Chopin's handwritten manuscript.
(Image source: Chopin Variorum Edition
The ritardando and "extra time" coming out of it can be heard, for example, in Evgeny Kissin's recording: