TL;DR: The Last Kiss has a fun horror idea and enough decent moments to make it an easy watch, but it doesn't do enough with the concept to really stand out - the mix of teen horror, supernatural mystery and death predictions works reasonably well, but the movie feels fairly familiar in places.
The Premise Does is Interesting
The strongest part of The Last Kiss is the central concept, and what made me want to watch it to be honest - being able to see someone's death from a kiss gives the movie an obvious ticking-clock element, and that can work really well in horror, but the concept is also where I kept wanting more.
There are plenty of ways the movie could have made this ability more disturbing or unpredictable, but I don't think it always took advantage of that, as while it has a good horror hook, the execution is fairly safe, and for me, The Last Kiss is more successful when it leans into the mystery and suspense than when it tries to bring in the horror.
It does feature some creepy moments, but this isn't the kind of horror movie where you're going to be hiding behind the sofa - the tension comes more from knowing that something bad could happen and trying to work out what the characters are going to do about it, and that's not a criticism on its own, but anyone going into this expecting something particularly dark or intense might find it a little lightweight.
Saying that, it is a teen horror type film, but it could have been more.
The Teen Horror Side Is Fine, Though
The teen setting works well enough though, with a familiar quality to some of the characters and situations, and the movie knows roughly what sort of horror it is and doesn't spend too much time trying to pretend it's something completely different, but at the same time, it doesn't really bring anything especially new to the teen horror formula.
That's probably the biggest problem throughout The Last Kiss - there's enough here to keep you watching, but it's also one you will probably forget about rather quickly.
The biggest issue around that though is that the actual horror is pretty inconsistent, as while there are a few good moments, featuring some sequences that work reasonably well, other moments are much more predictable, so when it wants to give you a scare, it generally goes for fairly familiar horror techniques.
Again, that's not automatically bad, as sometimes a simple scare works, but personally I just wanted a little more creativity from a movie that has such a potentially interesting central concept.
It Keeps Things Moving
One thing I will give The Last Kiss is that it doesn't feel unnecessarily bloated, nor does the pacing drag, as the story keeps moving, and there is generally enough happening to stop it from becoming a slog, so even in the weak moments, it at least moves along quickly.
The Last Kiss does have some explanation to get through too, but thankfully it also doesn't completely bury itself under constant exposition, which is always annoying, but you will always keep coming back to the main issue here while watching it, which is originality, or lack of.
The film is also caught between being a horror movie and a supernatural teen thriller, and as said, it has enough darkness in the concept to be much darker than it actually is.
Final Thoughts
The Last Kiss is a half decent popcorn watch that gets by on a good central idea and a reasonably brisk pace, but it doesn't do enough with its concept, and is a bit too familiar - I wouldn't put it anywhere near the top end of teen horror, but I also did not think it was a complete waste of time.