The original John Wick was the story of a heartbroken man with a borderline supernatural talent for killing people. He was trying to avoid using those skills, until a fool steals his car and shoots his puppy.
The next hour and change where Keanu Reeves, as John Wick, shoots about 80 people in the face... well, it's justified.
They killed his puppy.
But the revenge was had, the villains killed, the story ended.
And then, it became a hit. (On to Wick 2, after the break!)