My understanding (and I use the term in its loosest meaning) is that this was a summarising 2 hour movie, cobbled together from bits and pieces of Athena Goddess of War: a 20 episode South Korean TV series, which was itself a spin-off/sequel from an earlier TV series called Iris. You don't have to have the reviewing experience of Roger Ebert (just basic maths alone) to tell you that trying to compress 20 hours of storyline into 2 isn't going to be easy. And so it proves.
Suffice to say that there is a huge cast of characters, with most playing good and bad agents. Rather comically they just about all appear to be around the same age, i.e. 25. There's a professor, an agency head, oh yeah and the South Korean President who are about the only ones older. And most of the time they all try to kill one another. Any way that's the way it seems.
The good guys work for the NTS and the bad guys work for Athena and the good guys are always trying to stop the bad guys from carrying out various nefarious activities such as kidnapping the President's cute daughter. Complicating things for the NTS is that they unknowingly (until well into this film) have been infiltrated by a couple of Athena double agents.
I really don't think it's spoiling to say that the conclusion sees an ambush and a huge shootout, resulting virtually in both organisations probably not needing to worry about balancing staff leave rosters in the immediate to long term future.
This movie seems to have a body count of close to 500, seriously, but its all pretty much good, clean, very derivative, action fun. Every so often, to lighten the tone a little, a female agent and a male agent look at each other longingly and lovingly and the soundtrack suddenly soars with strings, to heighten the romantic feel.
If you feel like attempting to get your head around something different, which at the same time is trying to be very run of the mill, this may be your bag. I reckon it's where Austin Powers and Johnny English go for out of hours training.