Mercenaries 2: World in Flames

It is recommended that you do HVTs as soon as you can for each group. If you don't, part of the map gets blocked off and anything that was in that area is no longer reachable.

For this achievement, you can either capture the HVTs or verify their dead body. Capturing them is highly recommended as you will get more money and be able to get the Aces High secret achievement. Check that achievement on tips and tricks for it.

Note that there are 4 HVTs that can only be gotten during missions. However, only 3 can actually be captured as 2 of them are on opposing missions. As such, the achievement will actually unlock at 55 HVTs (which would be why it says 55 total on the progress screen instead of 56).
Also note that the final mission contains one of those HVTs, so make sure you have 54/55 before taking it.

The Aces High achievement is below if you wish to have further details on it.


Please note this is a very glitchy achievement. It has given problems for both me and many others. Please check the comments for more details.

This soution is more for those who like their achievements time-stamped (like myself). Seraph's guide is excellent and contains pretty much everything you need to know. Having read it and the numerous comments, I wanted to find a way to pop this achievement online. I'm happy to say this worked first time. Here's what I did (Warning: mild spoilers):

-Firstly, and mainly, play through the game as if you're going for the Aces High achievement (capturing all HVTs alive) on your playthrough. This can be frustrating as these guys have a tendancy to die from grunts, wayward explosions, and their own stupidity. I personally turned off auto-save so that if I was killed while trying to capture one, I'd know he wasn't unknowingly killed when the medevac transported me to the base.

-Make sure you have a save just before starting the Battle for Caracas where you choose siding with either the AN or the Chinese (I believe it's their third mission). This mission will have an HVT part to it. This particular target should actually be killed and verified via photo.

-As you continue through this mission, you'll eventually reach the end that has a cut-scene where the achievements pop. After that and credits, the game will create an auto-save and take you back to base. Quit out to dashboard and delete this auto-save.

-Now relaunch Mercenaries 2 and it will load your most recent save which should be before the Caracas mission. This time, capture the HVT alive. Continue playing through until the end. You should at one point see a different cut-scene. This will now unlock the Aces High achievement.

The downside to this is that you have to play the final mission again, making sure the HVT doesn't die. But I think it needs to be done this way because the achievement coding got screwed up in an update. The two HVT achievements are essentially story achievements (in that they have different cut scenes). But the unlock requirements have to be in order and only one "story" can happen at a time. Thus, if Aces High unlocks first, it assumes that you also unlocked ...And Justice for All so you can't unlock it unless you remove the update. However, you can capture them all alive after verifying all of them. Strange, I know.