Achievements

The Return of Demon Lord
"It comes out that this is legendary Demon Lord."

This achievement is unlocked by defeating the Demon Lord in the tutorial.

Forest King
"Defeat the Devil Lord in the Demon Forest."

This achievement is unlocked by defeating Swet • Hani for the first time.

Follow the Wind
"Defeat the Racing Master in the Demon Forest."

This achievement is unlocked by defeating Sibyde • Cat for the first time.

Castle Overload
"Defeat the Devil Lord in the Ghost Castle."

This achievement is unlocked by defeating Pernice for the first time.

Oppose High Tech
"Defeat those Mysterious Robots wandering about Ghost Castle."

This achievement is unlocked by defeating RM for the first time.

Robot War
"Have witnessed a battle for scrap recycling.  ''

beat post rm with rm and only robots

Lava Land Conqueror
"Have defeated the Devil Lord on the Lava Land."

This achievement is unlocked by defeating Kaos • Gut for the first time.

Pay a Tribute to the Human Hero
"Have defeated the arrogant human hero."

This achievement is unlocked by clearing all maps (including post-game maps). This one is not unlocked by defeating Lakemeng. It's highly likely that this one unlocks after getting 20 achievements.

Friend of Demon Pet
"10 types of demon join your allies."

10 monsters join you. Unlocks naturally.

Demon Pet Collector
"20 types of demon join your allies."

20 monsters join you. Unlocks before post-game.

Librarian
"Obtains an ancient book that should not be read."

During post-game, if you get every monster, you're given a new monster named "Devil Book" which can summon enemies during fights if it's on the battlefield.

Glutton
"Have gathered 777 Devil Fruits in total."

Have a total of 777 food items collected. This is not cumulative. You have to wait and do not feed any items until you have 777. A battle against Swet • Hani gives you about 200 Devil Spirit Puddings alone.

One Pudding is Enough
"Prevent any Slime to split in one battle."

I would recommend using Level 2-ish Frost Mages on the second map. However, it seems that you can't receive the achievement if any Slime dies.

Nightmare Just Begins
"Succubus lets 3 enemies charmed at the same time in one battle."

This is one of the few achievements where occasionally the game will glitch and not give you the achievement.

Take Care of your Cavities
"Prevent any Candy Slime to trigger Restoring Effect in one battle."

Getting this achievement is actually pretty difficult. Candy Slimes heal the hero when they are damaged so you need to win the mission without actually killing any Candy Slimes. Might force a few resets depending on where they spawn and how fast they do. I would suggest starting with Giant Screws and Milk Mums on every lane. Don't bother trying to do this on anything that's not a hero vs hero since you need to kill everything for the quests without a hero.

See Her Die
"Kill the Slime Queen while some Slimes still survive."

On a map with Swet • Hani, focus your attack power on two lines and play defensively on the third line.

Lightning War
"Finish the battle within 1 minute."
 * Use RM (doesn't matter what level)
 * Have at least a level 5 Zealot Demon on your team
 * Play the map Inventor's Hideout (which is left of the two Sibyde • Cat maps, post-game)
 * Deploy Zealot Demons on the uppermost attack line as soon as available (the cooldown time for these monsters is exactly how long it takes to gather 12 points)
 * Use RM's Grenade Launcher after 30 seconds
 * You have to defeat Sibyde • Cat before the Grenade Launcher can be activated a second time
 * If you still have problems, use level 6 Zealot Demons

Protector of Demon World
"Our alchemist has synthesized a hefty guy."

Use Research to build Claymore Armour.

High-End Toy
"This is the thing I have been longing for since I was a child.

Use Research to build Tank.

Ancient Protector
"Nobody has ever seen it......"

Use Research to build Masked Giant.

Behemoth's Shadow
"The Return of Nightmare."

Use Research to build Pallas.

Treasure in the Dragon Cave
"Its mum must be still searching it."

After getting 30 achievements, you unlock a monster called "Dragon Whelp". As soon as you get Dragon Whelp, this achievement unlocks.

Imitation Talent
"I have always imitated, but never tried to exceed."

Use the Myth Creature to copy most types of units. You cannot copy the Robot Bomb (will explode immediately), another Myth Creature and the final unit (does not appear on any map). Hence, 22 units have to be copied. Upgrading the Myth Creature makes it easier to approach units with long range attack. Some units like the Masked Giant have to be approached in-between two attacks.

Elite Forces
"One Military Unit has been upgraded to the top level."

Fully upgrade one monster. Some units like the Robot Bomb or the Giant Drill only cost a few thousand EXP for the final level up. In contrast, the Masked Giant needs 34,000 EXP for the final level up.

Super Power
"Fifteen Military Units have been upgraded to the top level."

Fully upgrade 15 monsters.

Demon Lord's Bodyguards
"All Military Units have been upgraded to the top level."

Fully upgrade all 25 monsters.

King of Demon God
"One hero has been upgraded to the top level."

Fully upgrade one hero.

Lord of Demon World
"All heroes have been upgraded to the top level."

Fully upgrade all 7 heroes.

Perfect Victory
"Win the battle without any death of allied units."

After you defeat the game, go to one of the first levels in the game.

Doctor of Demon World
"Have experienced all kinds of adventures in Demon World."

Simply beat all 36 maps in the game.

Victory of the First Battle
"Win one battle."

Win one battle.

Guard Regiment of Demon World
"Win 30 battles."

Win 30 battles.

Special Forces of Demon World
"Win 100 battles."

Win 100 battles.

Dangerous Area
"Be defeated in one battle."

Lose one battle.

War of Gentlemen
"Win the battle without any death of female devil when female devils are summoned for the battle."

Play the very first map and deploy a level 2 Demon Maid on the bottommost row. Do not send any more Demon Maids or Succubi and win the map.

Accurate Crit
"Using Robot Bombs for attack in one battle doesn't deal any damage to allied units."

You have to attack a hero. Attacking enemy units does not count.
 * Play the map Inventor’s Hideout, which is the left of the two Sibyde • Cat maps (post-game)
 * Deploy a Robot Bomb on the upper line and wait until it damages the hero
 * Now win the map. Do not use more Bombs.

Impregnable
"Win the battle when 3 battle lines are all protected by drills."

You need to have a Giant Drill on each line by the end of the match. Do not use an easy map, because your first Drill may reach the end before you were able to deploy the third Drill.

Has Been a Super Star
"Use the Dragon Whelp to eliminate 3 enemy units in a battle."

Dragon Whelps are weak but cheap to level up. You'll easily defeat 3 enemies with this unit.

Super Star
"Use the Giant Dragon to eliminate 10 units in a battle."

"Giant Dragon" is referring to Pallas. This is one of the few achievements where occasionally the game will glitch and not give you the achievement.

Hateful Fireman
"Frost Mage dispels the burning effect of one ignited target in one battle."

You have to attack a burning enemy (while the enemy is red) with your Frost Mage. You could use Dragon Whelps but I suggest Kaos • Gut's third ability, since it can instantly burn all enemies in one line. Simply use it before your Frost Mage is in attack range. Make sure the enemy does not die before the Frost Mage can attack. The enemy should not be a robot or another enemy that is immune to status changes.

Idol of Demon World
"After protecting the hero once time, kills three enemies and deals damage to enemy heroes."

This description was affected the worst by the translation issues. Despite myself having the achievement, I have no idea how to obtain this achievement. EDIT: Level up a Demon Maid to 6. Her new form shall match icon for the achievement. Go to a level where you fight a hero (for me it was Enemy Hero Routed) and kill three enemies and damage the hero.

I Love Iced Pudding
"Kill 3 Slime Devils entrapped in the ice in one battle."

Simply kill 3 Slime Monsters trapped in ice by Frost Mages. This is one of the few achievements where occasionally the game will glitch and not give you the achievement.

Psychologist
"Dispel enemies' Berserk Effect once in battle."

Muscular Soldiers have the Berserk Ability (when HP is lower than 30%, this unit will do double damage for 20 seconds.) So this unit needs to be alive for 20 seconds after being heavily injured. Use weak units to lower the unit’s health and let him attack your hero for 20 seconds. You could use a Giant Drill to prevent damage.

Betrayers Must be Executed
"Kill 5 apostate Slimes in one battle."

You have to face Swet • Hani. All of your Slime Units will turn on you after a few meters. Simply kill 5 of the betraying Slimes. This is one of the few achievements where occasionally the game will glitch and not give you the achievement.