Taken from my walkthrough. You can easily get 10 or 11 achievements in a single local game:Start a local game with a total of 3 local players, all of which are human. Place all your main account’s troops (player 1), in North America and in South America, with the exception of Brazil. Place all of the troops of the other 2 players in the rest of the world (also 1 in Brazil). Make sure that both player 2 and player 3 do not own an entire continent. Add all of the additional troops which you get somewhere in South America for player 1 (all in 1 territory), and somewhere in Asia for player 2 and 3. Whenever it is player 2 or 3’s turn, add all of the troops somewhere in Asia and skip. When it is player 1’s turn, add all of the troops in the territory in South America, and attack Brazil.
The Be the Best achievement in Risk worth 27 pointsAttack with 10 or more troops Then capture as much of Africa as possible, and skip your turn. Next few turns, let player 2 and 3 attack each other, and conquer both Africa and Europe with player 1. Since you will always attack with 3+ vs 1, you should unlock this achievement sometime.
The Perfect! achievement in Risk worth 25 pointsConquer a territory taking no casualties In turn 4, you will get this following achievement.
You should now have had around 4-6 turns.
Now capture at least 1 territory each turn until turn 9, but make sure you keep at least 7 hostile territories. Make sure you capture Australia in these turns, as this will give you another 2 bonus troops each round. Also do not use your cards yet!
In turn 10, trade in all of your cards, and place all of the troops you get in territories next to hostile territories.
Now conquer the remaining 7 territories to win the game.
The Breakthrough achievement in Risk worth 59 pointsConquer 7 or more territories in one turn