In "The Tempest", what did Antonio feel toward Prospero, and why?
Prospero, who was the Duke of Milan, had become obsessed with magic, and was not really attending to his dukely duties. In fact, he had given them over to his brother, Antonio, as he tells Miranda in Act 1, Scene 2
My brother and thy uncle, call'd Antonio...
...he whom next thyself
Of all the world I loved and to him put
The manage of my state...
The government I cast upon my brother
And to my state grew stranger, being transported And rapt in secret studies.
Antonio, who (to be fair) was doing all of the work anyway, started to think of himself as the duke:
He being thus lorded...he did believe
He was indeed the duke... he needs will be
Absolute Milan. Me, poor man, my library
Was dukedom large enough.
The King of Naples, who was an enemy to Prospero anyway, listened to Antonio, and the two of them decided to throw out Prospero and make Antonio the duke:
The King of Naples, being an enemy
To me inveterate, hearkens my brother's suit;
Which was that he, in lieu o'th’ premises
Of homage and I know not how much tribute,
Should presently extirpate me and mine
Out of the dukedom, and confer fair Milan,
With all the honours, on my brother...
And Prospero and the - then baby - Miranda were smuggled onto a boat and dumped on an island. And they've been there several years before the play even begins.