There isn't a single wasted moment in it. There is not one scene that does not bristle with energy and is not stylishly shot. There is not one action sequence that is anything less than jaw-dropping.I'll also note I find the title - "Chapter 2" of interest. While it could simply be a stylish way to designate the sequel without using a cheesy title ("Die Harder") or just the number, there's a theory going around places like Geek Gab, and from the structure of the two films, I give it credence, that there is an overarching story here. The second certainly sets up not only a future sequel but - giving enough of a climax to close out the movie - puts the pieces in play to finish an arguably ongoing story that ties neatly into the first.
About the only flaw that I can find in the movie is that maybe the characters are not particularly well developed or interesting- but that is because, one way or another, they are all going to get killed to death by the walking incarnation of the boogey man himself, John Wick.
Speaking of the titular character- I don't know how Keanu Reeves has managed this late-stage career change, but whatever voodoo hoodoo he do, it's bloody well working.
Long gone are the days when you could think of Keanu Reeves as the stoner chucklehead from Bill & Ted's Excellent Adventure. Gone, too, are the days when you could think of him as just another good-looking square-jawed Hollywood action hero from Speed.
Also, as the Didcat points out, there's an excellent writeup at Return of Kings. There are few films I consider "perfect" or nearly so, where everything fits, even the twists, where the acting just works, and the characters, editing, what is show on screen is done with absolutely minimum waste of time and a maximum of information, regardless of whether it pushes the boundaries of cinema or not. One for me is the Usual Suspects. One that looks like it may plant itself there is the recent Baby Driver. the first John Wick is also one.