For this achievement you are supposed to score 2,000 points in Score Attack mode, but when I was going for this, no matter how many points I got in a round, it wouldn't give me progress towards the achievement. For me, the only thing that worked was completing a round. So, I think the achievement is not for scoring 2,000 points, but for completing 2,000 games.If you have completed "NEEEEEEEEEEEERRRRRRRRD!!!!!!!" you will have 50% progress towards this
From the main menu, load up Versus > Score Attack
Lives: 1 Life
Time: 1 Minute
Versus type: Free for All
to Join, then
3 times to add 3 AIs
Select "Asteroid X" > ClassicAI kills count towards your progress.
The game ends as soon as someone gets a kill, which usually takes about 10 seconds. You'll get about 12% progress per hour.
This will get you halfway to