In this chapter, which describes how the Animals take over the farm and begin the process of doling out the work load, Boxer, the plough horse, is described as the hardest working of them all even though all animals did their part to the best of their abilities. Orwell describes Boxer as follows:

Boxer was the admiration of everybody. He had been a hard worker
even in Jones's time, but now he seemed more like three horses than one;
there were days when the entire work of the farm seemed to rest on his
mighty shoulders.

Boxer often does the work of several animals. He volunteers to do extra work, he makes arrangements to get woken up earlier than anyone else so that he can work a longer day. In short, he is the picture of dedication doing his part and then some so that those who are more limited in their abilities might have their needs met as well. He is altruistic and in it for the good of the group, not for personal glory. His motto was always

I will work harder

and he lived this motto daily.