Warhammer 40,000: Dawn of War II

You level up much like in the original campaign except this time you can reach level 30. You should be able to get this easily before the end of campaign, but if you having trouble there are items that add leveled characters, which you can pick up through out the game. You can also gain EXP from disposing of unwanted items.

As stated this is not available to guests, so if your playing co-op and your friend is hosting you will not this achievement.