This achievement is completed upon defeating the final boss at 5-10.
For this guide, I will give you a brief rundown of how to make this easier on yourself.
-Always use sunflowers, not sun-shrooms.
-As you progress, start making two columns of sunflowers 4MAXCA$HMONEY.
-Use the peashooters as placeholders to kill pre-wave zombies, but then replace them with snow peas as soon as you can
-When using chompers, pair it with a wall-nut/tall-nut right in front of them. (The chompers can reach past one space ahead of themselves to eat an opponent.)
-The minigames sprinkled in throughout the adventure mode are easy. So don't worry about those.
-Keep an instant seed packet (cherry bombs, jalapenos, doom shroom, squash) with you for each level
World 1: Day
Nothing special for these levels.
One column of sunflowers, one or two column peashooters, and some wall-nuts if you have to. When you unlock the snow pea, use those instead of the peashooters.
World 2: Night
You can't get CA$HMONEY, from the sky anymore. But that ain't no biggie, you don't need no sky money.
Place puff shrooms 4 spaces away from the right edge of the screen to fend off the zombies while you construct your sunflower columns. Now keep placing additional puff shrooms behind the original column.
Once you gather up enough CA$HMONEY, place snow peas in front of your sunflowers and place repeaters after that. The levels will get significantly harder around here, so don't be afraid to put down another row of repeaters or wall-nuts.
Also, use hypno-shrooms to convert some of the special zombies to your side.
You can dig up your puff shrooms to accommodate your new plants.
World 3: Pool
Now you got a pool, but not a fun pool. It's that kinda pool that always has a dead mouse at the bottom of it.
Anyway, you don't have to worry about any pool zombies early in the level, so just keep doing what you were doing.
When you acquire enough CA$HMONEY, use lilly pads to place your plants in the pool just how you've been doing.
Snorkel zombies will attack, so place a wall-nut on a lilly-pad in the pool halfway down the lawn. They'll poke their heads out to make out with your nuts, so the snow peas and repeaters will lay waste to them.
When the zombie cars start showing up, use spike-weeds to pop dem tires.
World 4: Fog
Now it's all foggy and spooky, but don't let that bother you! The fog is your BITCH!
Do the same thing here as you did for World 2 & 3, just guess and place where your plants need to be.
A new enemy comes up here. It's a balloon zombie that floats to you. At first you'll need to use cactus to kill them, but just use the blover on them when you get it.
You might need to start pairing up chompers with your tall-nuts during this world.
Magnet shrooms become useful at the last levels here as well.
World 5: Roof
This is a simple world:
1st column: Sunflowers
2nd column: Sunflowers
3rd column: Cabbage-pult
4th column: Cabbage-pult
5th column: Chomper
6th column: Snow pea
7th column: Tall-nut
8th and 9th columns are for cherry bombs.
When you unlock corn catapult use that instead of the cabbage.
Halfway through each level, when CA$HMONEY isn't a problem, replace the 2nd column with catapults.
Meh, it's just a slightly more challenging conveyer belt minigame. You'll be fine.