There are many ways to express what you have mentioned above. For example:
"Whoever ate the last slice of pizza..."
"Whoever finished the last piece of pie..."
"The person who finished last..."
"The person who ate it last..."
"The person who borrowed this book most recently..."
"The person who put this book over here..."
If you'd like to phrase what you are saying in question,
"Who was the last person to finish it?"
"Who was the last one to eat this?"
"Who was the last one to put this book over here?"
"Who was the last person to clean the room?"
"Who is the last person to have served in the company?"
Whoever is not exactly accurate, but you can check in the English Only forum.
I believe the best translation is "The last person who", like:
The last person who ate, the last person who borrowed this book, the last person who played
And also "the last peron to". Which has the same meaning as the above, except that "the last person who" is to be followed by a verb, while "the last person to" is followed by the infinitive: the last person to eat/borrow/play...etc.