After his wife's death, John receives a small puppy named Daisy in order to cope and provide the company to not grieve alone. At the end of the movie, after finishing his final act of retribution, John takes with him a stronger built pitbull puppy, and heads home.
Was this an intentional act of symbolism; with his first dog a representation of his fragile state after Helen's death, and the last dog a representation of a stronger, more willful John Wick?