What details make Boxer's death so tragic?

Boxer's death is one of the most tragic events, if not the most tragic event, in the book.  There are a number of reasons why. 

First, Boxer is one of the most loyal animals on the farm.  Moreover, he worked harder than any other animals.  At times it seemed like he worked more diligently than all the animals combined. According to the text, Boxer's motto was "I must work harder." Here is what the text...

Boxer's death is one of the most tragic events, if not the most tragic event, in the book.  There are a number of reasons why. 

First, Boxer is one of the most loyal animals on the farm.  Moreover, he worked harder than any other animals.  At times it seemed like he worked more diligently than all the animals combined. According to the text, Boxer's motto was "I must work harder." Here is what the text says:

His answer to every problem, every setback, was ‘I will work harder!’ — which he had adopted as his personal motto.

Second, even when Boxer was aging and his body was failing, he still worked with all his might.  This quote says it all:

At such times his lips were seen to form the words, ‘I will work harder’; he had no voice left.

From these words, it is clear that Boxer gave everything he had; he completely sacrificed himself.  He was also sincere in his labor, and he sincerely believed in the rebellion. 

In view of this fact, the tragedy was that he was laboring for a lie.  Moreover, when he could no longer give anything, he was betrayed by Napoleon, who sold him to the knackers.