Who did the animals admire the most?

That would be Boxer the horse. His two slogans are “I will work harder” and (later on) “Napoleon is always right.”

In chapter 1 of Animal Farm, the horse Boxer is described as a huge strong horse.

[In] fact he was not of first-rate intelligence, but he was universally respected for his steadiness of character and tremendous powers of work. (ch 1)