Vera and John, you both point out a critical aspect of revenge movies: We need to connect to the Protagonist's emotional condition. If we can relate to their pain and anger, great. If not, all of the acts of violence perpetrated as part of the revenge plan are just noise.

I'm not a big action movie fan, but I did like John Wick. I got the transference of affection for the puppy as symbolic of his deceased wife. The fact the dog showed up *after* she died gave the puppy a kind of supernatural quality. So the death of the dog is not just about it being a dog, it is about his wife dying *again* and whatever hope John had of spending years with his wife via the puppy were squashed by the dog's death.

Plus, it's a puppy who gets killed. That's enough right there for me to want John to get revenge. All the other psychological associations make his motivation even that much more evocative.

Takeaway: What you say--emotional connection to the character seeking revengs is critical.