Answer:
Resentment, bitterness.
Explanation:
The word "grudge" means holding some sort of resentment against someone. It is used in a negative sense.
In the given context, the word is used to describe the situation or relationship of the two families of Capulets and Montagues in William Shakespeare's "Romeo and Juliet". And so, considering that the underlined word is "grudge", we can safely assume that the word connotes "resentment, bitterness" etc.