Mercenaries 2: World in Flames

Note: I suggest doing all this before you complete the battle for Caracas because I am not sure what cannot be done after as the area around the AN or China's HQ is not accessible.

Simple list:

-All 10 HVT's for each faction (mission based ones don't count)
-Kill 50 opposing faction members for each faction (except pirates)
-Destroy 40 billboards for the PLAV
-Capture all outposts for each faction
1 for PMC
3 for Pirates
4 for PLAV and AN
5 for China and UP
-Destroy all buildings for each faction
-Complete each factions side missions at lvl 3 (lvl 3 Must be completed)
-Complete the game (this will net you the nuclear bunker buster)
-Collect 100 spare parts (see below for glitch)

Now I'm not sure this will work for everyone but it worked for me and a friend connected to live with the most recent update. Once you have collected 32 of the parts (see tinyurl.com/6lwo59 for a helpful map) once you quit and reload the parts you collected will allow you to collect them again.

Best part is you can just fly over them to collect them. The on screen prompt won't tell you the right number, but if you go to the progress screen it will tell you how many you have. I personally have over 130 they keep adding money for every one.

So just find 10-15 that you can remember there locations and save, quit, reload and you'll be there in no time.

If you vote negatively on this guide please leave a comment with whats wrong and ill be sure to help fix it.

Before you start your playthrough, TURN OFF AUTOSAVE!!! In place of it, get in the habit of saving before and after each level of each Challenge, before and after each destruction Target, and before and after every HVT and faction mission. Save each time to both your hard drive and to the Cloud. Ideally, keep saves on a key drive. There is a limit for how many saves you can have for this game, as I discovered. You will at some point have to overwrite a save file, so be sure to also have pen and paper handy to take notes on what is going on in-game on each save file. You will inevitably either get overconfident and make a major mistake and have to backtrack, or you will encounter severe bullshit to include HVTs killing themselves.

For efficiency, go for Aces High and Digital Man in the same playthrough. Do only one faction at a time. First mission, then destroy all targets, then capture all HVTs, then then do the outposts and Challenges, and then finish off any remaining missions. After each outpost, be sure to buy the PMC Fuel capacity upgrade.

Do the Factions in this order: UP, Communist rebels, Pirates, and then stop. Once the Pirate faction becomes available, go around and grab as many of the spare parts as you can. Enough of the map will be open to allow for that. The spare parts glitch still works as of September 2022, and I only picked up about 50 (saving after each one) before quitting and reloading the save file. The ghost parts respawned invisibly and can indeed be picked up merely by flying or driving near one. I ended my playthrough with over 200 without trying.

Once the spare parts are done, make sure all the Pirate Challenges are done BEFORE initiating the Blanco mission and the Introduction to the AN and China dialog. The Pirate Challenges are some of the worst torment ever featured in any videogame if you do them later, but they're shockingly easy if you do them early on before the AN and China are on the map. All you have to do is honk your horn near any hostile unit (they'll only shoot off a few small shots) and drive carefully. Just also be sure to bribe the UP so that they're friendly before you do the Pirate Challenges.

Once all the UP, Rebel, and Pirate Challenges are done, and all their Targets destroyed, and all their HVTs captured alive, then bring in the AN and China. Do the AN first, same procedure as above, but DO NOT START THE BATTLE FOR CARACAS. Leave that undone. Go and start the Chinese mission, then do the Targets and the HVTs, then the remaining Outposts and Challenges and of course the Fuel Upgrades. You do not have to do any of the remaining Chinese missions. The AN will be Hostile to you, so go back to the PMC and bribe them back to Friendliness.

You should be at 164/165 Shop items, and 53/55 HVTs. Side with the AN, and use the Ambassador Gunship to easily take out the Chinese targets and SAMs and land nearby General Peng outside the Chinese Headquarters castle and capture him. It's not too difficult to get the AN pickup chopper to land on the castle arm itself.

And then, you go after Solano. Use the Ambassador Gunship to have an easy time taking out the copters guarding his bunker and to clear the ground before aiming the nuclear bunker buster. The Digital Man cheev and the Aces High cheev only unlock AFTER Solano is captured.

And if you have trouble with the Chinese HVT on the oil rig, use the Ambassador Gunship to easily take out the guardian helicopter, then land on top of a crate near the suited HVT (so the soldiers can't hop into it and ruin everything for you), jump down, kill the handful of soldiers, subdue him, call in the pickup, and it should be fairly easy.

These side missions must be completed before either AN - "The Battle for Caracas" or China - "Exit Strategy" as these will be unavailable after the final mission.

PLAV - Jungle Cruise
AN - Give it a Whirl
China - The Last In Line
China - Medusplosion

Also for clarity:
You do NOT need to do any Mercenary challenges. All the shop unlocks come from hidden packages.

I made this second solution so it doesn't get lost in the comments.