Overlord II

ok so the easiest way to get this is to set up a ranked match and have a friend join you once your in the game grab 10 minions and jump in the boat and grab some treasure the second your winning have the other player quit repeat this ten times and eventuly the achievement wil unlock it took me and my friend 10 minutes each to get it. this is your best chance of getting it because no-one else plays it online anymore.
UPDATE:method no longer works so youll have to do it th old fashioned way sorry guys but just grab a friend and play through 10 levels all the way
ANOTHER UPDATE:some people are saying it works some are saying it doesnt just try it for yourself

Ok, this is a a basic strategy for winning a pirate plunder match.

Note: This strategy is written with the assumption that you are the red Overlord.

Getting a fast start is essential to this so as soon as the game starts loading start holding the left stick foward. Then, when you're loaded in run forward and spawn 10 reds and 10 browns. Now run to your ship and send your browns into the ship to row. After this is done place a guard marker with your reds in the middle of the ship and start sailing. Make sure to strike your drummer at every oppurtunity. To begin, sail forward and take a left turn and sail around the small circular island picking up all the treasure chests. Continue sailing until your heading back to the dock you started from. Keep heading that direction till you get to a small island with a rock fortress on it. Dock here and bring your browns with you. Clear out both of the rooms ( there are elves here) and break open all the treasure chests. Also make sure to grab the extra weapon in the second room by sending a minion to grab it for you. Sail off this island and continue to find treasure chests and attack your opponents ship at every oppurtunity. It also helps to defend your vault when your enemy attacks it at this time. At around the 2 minute mark sail around to the back of your opponent's island and dock there and use your reds to turn the wheel to open your opponent's vault. You want to use the reds here because they are impervious to fire damage which helps if your opponent is trying to use reds against you. Make sure to defend your reds with your browns if the enemy is attacking them with ground troops. When the doors are open run in there and pick up all the gold. By this time the match should be almost over and you should have a big lead so your opponent will not have the time to take it from you. If this is the case, do a victory dance to mock your opponent. It takes a little while to master but when you do master it, it always works.

No expecting any votes for this.

Get a friend or find a player willing to boost this with you.

Pick Ranked match, Pirate Plunder.

When the game starts get 20 minions - 10 brown and 10 whatever. Go to your ship and command your minions to jump into the hold - towards the front of the ship. To command your minions to do this press LT and RT ( Left Trigger and Right Trigger) until you have 10 minions in the ships hold.

Then move your overlord to the back of the ship ( there will be a white glowing ring). Stand in this and press A to get your minions to get the oars out. Then press RT to get the ship to accelerate. Steer the ship over some gold.

Get the other person who isn't getting the gold to quit out.

Do this 10 times each.

The quitting method stated by Conmacca still works as of 15th May 2013.