In the last few bars of Liszt's masterpiece, Liszt actually wrote a crescendo which can't possibly be played on the piano. I don't know how to interpret it. How do you approach it? Is that more of a gesture thing (like putting more weight on the keys after having played the notes)?
It's often not a bad idea to check whether or not IMSLP has an autograph for a piece in the public domain, or failing that, to check other editions. In this case, IMSLP has a holograph manuscript which shows the point of the crescendo distinctly to the left of the second chord. I would play the second chord somewhat louder than the first, and break right back to ppp for the third chord. The holograph is here.