Pyromaniac

Difficulty: Hard-very hard (Easy in Buttered Popcorn)

Pyromaniac is an achievement unlockable on iPhone, iPad, PlayStation Vita, Android, and Nook versions of Plants vs. Zombies. In order to unlock it the player must win a level of Plants vs. Zombies only using explosive plants to kill zombies. The easiest way to get it on the iPad version is by completing Buttered Popcorn.

Strategies
The explosive plants are: You can also use sun producing plants as they don't kill zombies, but Lawn Mowers, Pool Cleaners, Garden Rakes, and Roof Cleaners can't be used to obtain this achievement. You cannot use other instants (except the Coffee Bean) like Blovers, Hypno-shrooms, Tangle Kelp, Umbrella Leaf, the Squash, and Chompers. Generally speaking, anything that shoots the zombies are not allowed (except for the Cob Cannon, although you could theoretically plant and upgrade or dig one before it shoots). If you attempt to plant a Cob Cannon, it requires two Kernel-pults, so only plant them when there are no zombies in that lane or you won't be able to get this achievement because the Kernel-pults might kill a zombie.
 * Cherry Bomb
 * Potato Mine
 * Doom-shroom
 * Jalapeno
 * Cob Cannon
 * Ice-shroom

Note: Wall-nuts, Tall-nuts, Pumpkins and Garlic don't count as plants that attack zombies, as they defend. Graves don't count as zombies, so you can use Grave Busters.

You can get this achievement in Quick Play. The easiest and best way to get this achievement is in Level 1-1. Choose the Sunflower, Garlic, Jalapeno, Cherry Bomb, Doom-shroom, Imitater Doom-shroom, Coffee Bean, Potato Mine and whatever else you may want, that don't attack zombies. As the achievement states, you can only use explosive plants to kill zombies. Stockpile Doom-shrooms behind Garlic so they're safe you don't have to wait as long between uses. If you have shooting or lobbed-shot plants, you can't achieve this, but it isn't very different from any other level, so it can be beaten easily. Or just play 2-10 using only Doom-shrooms and Ice-shrooms will gain the achievement much more easily than another way. The main difficulty of this achievement is the recharge time. Whenever a huge wave of zombies appear, place two Garlic on two lanes, and use a Cherry Bomb to blow up the zombies, but you'll get Explodonator first, instead of Pyromaniac. If you see too many zombies, use a Doom-shroom to blow them all up, but when you're in the final wave, divert more zombies, and use a Cherry Bomb and get the Money Bag, and you'll achieve this. You may also want to use Twin Sunflowers if necessary to rack up your total sun. A word of warning - if you have bought the Garden Rake from Crazy Dave, you will not get this achievement until the rake disappears.

Alternatively, it can be easily obtained in Level 2-1. Choose Sun-shroom, Cherry Bomb, Doom-shroom, Wall-nuts, Tall-nuts, Pumpkins, Potato Mine and Jalapeno. Kill the first two or three zombies with Potato Mines, while building 4 lines of Sunshroom. As soon as zombies start to come faster, slow them down with Wall-nuts, Tall-nuts, and Pumpkins and use a Doom-shroom to reset the situation when you attain 125 suns. Continue to setup until you reach four lines of Sunshroom, then you'll have plenty of sun to spam Cherry Bomb and Jalapeno. When a line is quiet (no zombies) put a preventive Potato Mine. When there are many zombies on screen, Doom-shroom to reset. If you can, add an Imitater Doom-shroom for additional power, but the level can be won without it.

It's also possible to get this achievement in other Adventure levels, but it will be quite a bit harder. Imitater instant kills can help.

In Last Stand you get enough Sun to plant twelve Kernel-pults, six Cob Cannons, six Lily Pads, and twelve Wall-nuts. You can also get Defcorn 5.

Adventure Mode
Choose the following plants: As said before, you can only use explosives to kill zombies, so don't buy the Garden Rake and make sure no zombies reach the Lawn Mowers, Pool Cleaners or Roof Cleaners. It is recommended to do the level on 1-1, if possible, because it is the easiest level. At the beginning of the level, plant a Sunflower at the top left corner of the lawn. Whenever you can plant a Sunflower towards the left of the lawn, but make sure you don't go past the second column. When the first zombie comes, plant a Potato Mine or Imitatier Potato Mine ahead of him as much as you can. Do this for most of the zombies that approach. If there is a small group of zombies that you can't handle with Potato Mine, use a Cherry Bomb. If there is a lane with lots of zombies, use a Jalapeno. If there is a huge wave of Zombies, use a Doom-shroom and wake it up with a Coffee Bean. When you have around 700 Sun, plant a Kernel-pult, and quickly plant another in front of it, before they kill a zombie. Then, upgrade them to a Cob Cannon (don't do this until you have at least 700 Sun and the Cob Cannon is completely recharged). Using this strategy, you will probably win the level and unlock this achievement.
 * Ice-shroom.
 * Sunflower
 * Potato Mine
 * Imitater Potato Mine
 * Cherry Bomb
 * Jalapeno
 * Doom-shroom
 * Coffee Bean
 * Kernel-pult
 * Cob Cannon

Alternative Method (does not use Cob Cannon)
Choose to use the following plants: Do this on Level 1-1 or 1-2. Plant your Sunflowers in rows one and five, upgrading them when you have enough Sun. When the first zombie comes, plant a Potato Mine as far back to the left as possible. After you gain enough sun, begin planting Garlics in in column two of rows one, three and five. After this, begin to plant your stockpile of Doom-shrooms in row three, then in the empty spots of one and five. Use Coffee Bean to wake up a Doom-shroom, but remember not to go overboard and use Doom-shrooms to take out single zombies, using Potato Mines instead. Use the other instants when necessary, or when there are no Doom-shrooms. Plant Potato Mines, Wall-nuts, or Tall-nuts at the end of rows two and four as a last resort protection. After this is set up, the game is a cakewalk.
 * Sunflower
 * Twin Sunflower
 * Potato Mine
 * Cherry Bomb
 * Jalapeno
 * Coffee Bean
 * Doom-shroom
 * Imitater Doom-shroom
 * Garlic
 * Wall-nut or Tall-nut (optional)

Another strategy
Load out with the following: This strategy is best used in 1-1 or 1-2. Just plant your Sunflowers and Potato Mines as you normally would. Then plant Garlic in every row except one. This will force all the zombies into one lane, so you can roast them with Jalapenos.
 * Sunflower
 * Potato Mine
 * Garlic
 * Jalapeno
 * If you want, Imitater Jalapeno
 * Other explosive plants you find necessary

Note: If you are going to use Cob Cannons to complete this, you must upgrade it quickly so the Kernel-pults don't kill anything.

Wall-Not Attack and Pyromaniac
This will earn the Wall-Not Attack and Pyromaniac achievements in ZomBotany.

Plants:
 * Sunflower
 * Twin Sunflower (optional)
 * Garlic
 * Potato Mine
 * Cherry Bomb
 * Imitater Cherry Bomb
 * Coffee Bean
 * Doom-shroom
 * Ice-shroom (optional)

Plant Sunflowers in lanes 1, 3, 5 and two Garlics in front of each of those lanes. When a zombie comes, use Potato Mine. When there are more zombies, use Cherry Bomb and use its Imitater form when it is recharging. Use the Doom-shroom during every flag.

S - Sunflower

G - Garlic

C - spaces for Cherry Bomb and Doom-shroom

Easy Method
You can also kill a zombie with a Potato Mine in I, Zombie to get this achievement. The Potato Mine makes its debut appearance in I, Zombie in the level Can You Dig It?.

Alternate Easy version (iPad only)
Completing the minigame Buttered Popcorn will get you this achievement if you don't use a Garden Rake.

Trivia

 * This achievement does not appear in the Nintendo DS version of Plants vs. Zombies, because the Mini-game BOMB All Together! has a similar concept; however, a rake can be used in BOMB All Together!, despite not being an explosive.
 * The Mini-game Buttered Popcorn on the iPad version can be used to get Pyromaniac easily, as long as the player does not use a rake.
 * If the player would use Cob Cannons, Pyromaniac would be harder to achieve because the Kernel-pults are not explosives.
 * If the player hacks the iOS version of Plants vs. Zombies and enter Slot Machine with a type of sun-hack, there is a glitch where not only will the player instantly win the level but this and Good Morning will be achieved.
 * Tangle Kelp, Squash, and Chomper do not work because they are not explosive, even though they are instant-kills.
 * The achievement's name is based on pyromania, which is obsession to lighting things on fire.
 * This achievement is similar to the Fire Works achievement in Plants vs. Zombies Adventures.