ACA NEOGEO METAL SLUG X

In order to get this you will need to finish the 1st level with all POW's found and the usable vehicle intact. You also must complete the level without dying. If you die, you'll lose all of the POW's you've rescued up to that point. You need all of them to get the full bonus points at the end of the level. It might take a few playthoughs for some people to memorize enemy locations and attacks. Once you know the level it really isn't very difficult. Here are some things to do to maximize your points.

-Get all 12 POW's. The 1st 9 are out in the open and virtually impossible to miss. The last 3 are hidden during the boss battle. Once you damage the boss enough, it will raise up to reveal a gun turret underneath. Destroy that turret to reveal the final 3 prisoners.
-Around halfway through the level you can ride a camel with guns. Shortly after getting the camel you will come across a tank vehicle to use. Take it. Then you will come to a part where you have to destroy 2 missile launcher type vehicles and several enemies. As you kill the enemies on foot one will drop an item. Most of the time it will be a jewel that will give you 30,000 points. Sometimes it will instead be an apple that will give less than 1,000 points. You really want that jewel to have the best chance of success. If you don't get it I recommend restarting.
- Soon after that you will come across a group of helicopters. Only kill the red one in front. Killing that one will set off a chain reaction that will destroy the rest and give you a big bonus in points.
- On the boss only use the basic attack . It will take longer but will get you way more points. You basically get the same points per bit of either attack. The other attack is stronger and does more damage and will finish the boss faster resulting in less points. Basically going for hits instead of damage.
- Finish the boss with out dying, having all prisoners rescued and the tank vehicle intact and you will get a 540,000 point bonus at the end of the level.

If you do all of these things, you will have over 800,000 points at the end of the 1st level and all Caravan mode achievements.

Here is a video I recorded of me doing it. It wasn't my best run but is good enough to show people how to get this.

BrutalGuitar's solution is spot on but if you'd like to see a successful attempt in video form, check this out below:

This is a complete achievement walk-through with a successful 1.5mill run of HI SCORE MODE video with constant commentary explaining everything to look for when attempting these achievements. I can guarantee you will limit the amount of play-throughs needed by watching/reading this

ORIGINAL Mode: Use the walkthrough to see how to maximize points in the first 2 missions, then combine that with the save trick mentioned below to achieve 2,000,000 points.

CARAVAN Mode: "Get as many points as you can in 5 Mins" So basically follow the walkthrough for Mission 1 and these cheevs shouldn't be a problem.
*Can be glitchy I got 900k and only unlocked the 500k achievement...it wasn't until I "Quit" the game and reloaded it that it worked, but only after I reached the required score again.*

HI SCORE MODE: To get 1.5mill w/o continues...this is the main focus of this video follow the tips and watch the playthrough for your best chance at success. Practice makes perfect here!

*ALL TIPS / Text Guide*

TIMESTAMPS:
00:01 - Tips Explained
01:43 - Mission 1 Ended w/ 911,000 Points
06:02 - Mission 2 Ended w/ 1,474,000 Points
12:52 - Mission 3 Clean Up
15:47 - ORIGINAL Mode "Save Trick"