The Hangover Part 2 got a lot of flack when it first came out, as well it should have - it was a comedy that wasn't very funny. But I will give it this: it was a fascinating viewing experience because I can't think of many other movies which would try to get laughs out of such dark, dark places. The first Hangover mined a lot of it's humor from awkward or uncomfortable situations - there was a naked man in a car trunk, a stolen cop car, Mike Tyson's tiger and so on - but the sequel raised the stakes by repeating that plot exactly and then adding on an existential component. The first time those guys had a wild adventure they could claim that it was a drunken accident but the sequel was honest about acknowledging that their willingness to do those things a second time said something about their true character. Sure, the Hangover Part Two didn't necessarily wring a lot of chuckles out of it's chopped off fingers and dead monkeys, but I think you can justify the movie's entire existence based solely on the scene where Ed Helms' seemingly straight laced character gives a speech about how he must secretly love chaos if he keeps going out and creating it.
Unfortunately, Horrible Bosses Two lacks the Hangover Part Two's commitment to darkness. The first Horrible Bosses had some grim elements, but it managed to maintain a relatively light tone because it's trio of lead actors were all charismatic enough that you could kind of buy their nice-guy routine even as they were acting like monsters. That movie was about three men whose lives were being ruined by their (horrible) bosses, so they all came together to form a murder pact where they would trade targets under the theory that they could all get away with murder if the actual killer had no direct connection to their victim and if the person with the motive had an air tight alibi for the time of the crime. Horrible Bosses 2 doesn't repeat the first plotline exactly, but it has a very similar vibe. This time the three men have just started their own shower nozzle business, but a ruthless capitalist is threatening to steal it from underneath them... Unless they can kidnap his son and hold him for ransom. Kidnapping a fully grown man is not as bad as triple homicide, but coming on the heels of an attempted triple homicide it still looks pretty bad.
Horrible Bosses 2 does pay some lip service to the fact that these men cannot consider themselves to be good people after they've engaged in a murder pact and a kidnapping scheme, but it doesn't do nearly enough with that idea to justify this movie's existence. For starters, none of them seem to instinctively understand the implications of their actions - that has to be explained to them by Motherfucker Jones, the ex-con character played by Jamie Foxx, and even then they dispute the obvious. Honestly, their obliviousness is almost more upsetting than their actual cruelty, because it speaks to a certain type of entitledness that is (to me at least) harder to justify than violence. Someone might resort to murder or kidnapping because they feel like they have no other options, and that's awful, but I can understand it if it's framed properly; but anyone who claims that they "had no other choice" over and over again is obviously a lair and a psychopath, especially if they are making those claims unreflexively and without hesitation or guilt.
Now, I have a lot of thoughts on that particular form of entitledness, but I already wrote about them in my review of Let's Be Cops so I'd rather come at this from a slightly different angle here. Horrible Bosses Two's ethical problems can also be looked at from a Nietzschean perspective, specifically using his conception of the Eternal Return, where he says that the knowledge that you are repeating your actions is far, far more painful than actually having to repeat them. In other words, although the audience can be horrified at the thought that the Coyote is doomed to chase (but never catch) the Roadrunner our repulsion at the idea of his doomed existence is tempered somewhat by the fact that he doesn't seems to understand his own situation. It's quite different, however, when a protagonist gains sentience and some semblance of memory; then they have to come face to face with the fact that their lives are meaningless iterations of a simple repeating idea - that they are helpless against the whims of a fundamentally frustrating type of fate.
That's why the Hangover Part Two's darkness works (even though that darkness undercuts the movie's comedy) while Horrible Bosses Two's comedy doesn't work (even though many of it's jokes land.) The Hangover Part Two's was willing to examine itself in a fairly meta-way, and thus it ended up being an exploration of what living in a sequel would be like, and I thought that was compelling in it's own way. (I might have been alone in that, however, because it was, after all, building this repetition around Mike Tyson cameos so it wasn't exactly the brightest exploration of Nietzschean ideals imaginable.) However, Horrible Bosses Two's unwillingness to honestly address it's essential nature put it in a terrible no man's land where it wasn't going to be as funny as the original (which was, well, more original) nor was it going to be that interesting, since it was completely unwilling to look beneath it's own surface.
Of course, not every sequel is really an example of the Eternal Return in action - there are a lot of franchises where the characters evolve over time as people, and as they do so they find themselves in different situations. I would never talk about (say) the Before Sunrise/Sunset/Midnight movies this way because they don't repeat themselves in this same way. (Which isn't to say that they don't have their own existential problems - they just don't suffer from Nietzschean sequel-itis.) But there are a lot of franchises that are built around the idea that the same stock characters will find themselves in the same stock situations over and over again and that none of them will realize that they are stuck in an endless loop. The only way to make that palatable is to build the franchise around good people; while it's ridiculous that John McClane keeps accidentally finding himself in situations where he has to stop some terrorists, we can still find some comfort in the idea that good keeps triumphing over evil, but we would never accept a series where a villain went from movie to movie killing a new hero every time. Horrible Boss Two's problem isn't that it's a carbon copy, it's that it's a carbon copy that's built on horrible people. As someone - (Nietzsche?) - said: "commit one massive crime shame on you, commit two massive crimes and really, really shame on you."