Easiest method is to just log in a second controller. You will notice that it doesn't pop achievements during the points, but you can trick the game into thinking you scored that against the computer. Follow the below method for popping 200K, 300K and 400K achievements:
1. Change game settings to 4 second time limit (Game settings is available using the
button.) This step is optional, but it will make it go by a lot faster.
2. Start up the game and press
, then
on your second controller, this will enable a new challenger.
3. Kill the second controller in 2 matches (4 battles total), this will net you 200K assuming you got the perfect bonus killing the opponent (But why wouldn't you, lol).
4. Don't continue fighting your second controller, instead lose to the computer and hit
, then
to continue.
5. After continuing, select a character to use and initiate the battle against the AI (not second controller).
6. At the start of battling the computer, you will pop the achievement for 200K. Now, hit
, then
on your second controller to interrupt.
7. Repeat steps 3-6, but instead of 2 full battles it will only be one for 300K and do it again for 400K.
8. After losing to the computer and netting the 400K achievement, update high score and get those other two achievements. Now all you have is high score mode and caravan (assuming you did this bunch first)
If you already have the 200K and 300K achievements: Just battle the second controller until 400K (which is 4 full matches), then lose to the computer, continue and battle again to net your achievement.
Obviously you can get this just fighting the computer if you're good enough, but this is by far the easiest method because it only requires you to kill/fight non-moving opponents.
Hope this helps those who are tired of fighting those fast characters.