Who crushed Rize Tokyo ghoul?
She was one of the most powerful characters in the series and she proved that very often. She was able to fight against the likes of Arima and Kaneki throughout the series. Her regeneration powers were insane, as seen when she was able to regenerate her body that was destroyed by Furuta when the two fought.
Who killed Rize in first episode?
In the first episode, someone threw the crane in order to kill Rize, however that also prompted in having to save Kaneki from totally being devoured/killed . That was the point from where everything basically took off.
Who dropped the stuff on Rize?
In the Manga near the very end Tokyo ghoul, Kaneki remembers the incident, and it was shown that, The Ghoul Group called the clowns did it as One of them, Souta, was there.