Hammy acting all-round (Travolta's takes the cake though). Bizarre editing decisions. Broad sections of the movie are completely unnecessary (the several Psychlo-sponsored escapes leading to almost immediate recapture). Giant leaps are taken in the script. There are scene we are propelled forward regardless of whether anything makes any sense and often things are just left unexplained. Who's idea was it to film everything on a 45 degree angle?
But the special effects still hold up pretty well and somehow it's entertaining... though probably for all the wrong reasons.
There's some good stuff in this re-telling of the first tale that's for sure... but the whiplash-inducing editing undoes a lot of it (the good cinematography, the gore). That meltdown/transformation near the climax is the real standout of the whole thing. I'll say one thing: after the horrific Part 3, this cheapie was a treat!
First, the cons: it's a little too long for its own good and some of the characters are out-and-out annoying. I'm talking about you, Little Miss Know-It-All (blame the screenwriter for that though cause Joey King was fine for what she was given) and Jason Clarke's bad guy. He isn't intimidating so much as he is irritating (due in no small part to Clarke trying so hard to suppress an accent or a lisp or whatever that he winds up sounding like he constantly has a mouthful of spit and can't find a place to hawk a loogie).
But Channing Tatum and Jamie Foxx are charming (let's not forget to mention the character Donnie who is just the man) and it's pretty taut, especially towards the end. One thing this has over Olympus Has Fallen: a not-useless President.