Fiona's final line towards the dead Lorenzo, who betrayed her trust, caused the chain of events that lead to her parents dying, being forced into her new home against her will, resulting in her being chased by several people who tried to kill her, including Lorenzo, who pretended to help her escape.
Fiona: "This time...you really are dead. You bastard."
Hewie's sneak attacks take the cake here, especially when he jumps Daniella from some bushes and nearly severs her neck.
Also satisfying is smacking Riccardo around with sulfuric acid in the examination room. Have another facial scar, you raging bastard!
This can also be done to Daniella.
Daniella spends her entire portion of the game (or half, depending on if Fiona lets her pick up a poker) with a shard of glass in her hands. During her boss battle, Fiona will trigger some kind of magical hoopla that destroys the glass ceiling above Daniella. Guess what happens?
How can Fiona destroy Lorenzo's body? Let me count the ways...
"Shoot me all the hell you want, Riccardo. Your bullets cannot penetrate the fur of...STUFFED TOY HEWIE!!"
The first three endings are awesome moments themselves. Ending C, however, tops the list. Not only does Fiona find the castle gate key before anyone else can sink their claws into her womanhood, her ears are saved from the gargled screams of Lorenzo. She also misses the old man flinging himself down the stairs in an attempt to catch her. His wheelchair/throne lands on top of him. FTW!
The ending is especially cathartic after all the hell you go through just to complete the game once. Take that, Lorenzo!