Before getting start, open your save game location.

Windows: %APPDATA%\roaming\kingdom_rush_origins
Linux: $XDG_DATA_HOME/kingdom_rush_origins
Mac: ?

Open file name slot_1.lua

These achievements contain counter, you can modify its value to before the target. For example: Gnollum achievement require Defeat 100 Bloodsydian Gnolls., modify the value for GNOLLUM to 99 or less to get this achievement faster.

-------------------

ARCANE_BURST => Rambo Style
Defeat 50 flying enemies with Arcane Burst arrows.

ART_OF_WAR => The Art of War
Read all tip cards.

BEORNINGS => Beornings
Have 8 or more Runed Bears in any single stage.

BIGGER_THEY_ARE => The bigger they are...
Defeat 7 Golems before they walk past half the stage.

BLADE_DANCE => Tauriel Apprentice
Make 600 Blade Dance moves.

BONE_COLLECTOR => The Bone Collector
Collect 100,000 gold from defeated enemies.

CALL_ME_PIG => Call me Mr. Pig
Make the Razor Boars trample and kill 20 enemies.

COUNTERMASTER => Counter Master
Defeat 250 enemies while silenced.

DARK_CRYSTAL => Jurassic Lake
Crystalize a single creep for more than 10 secs.

DND => D&D
Have Beresad and Ashbite defeat 100 enemies.

DOGFIGHT => Dogfight Ace
Have your Gryphon Riders defeat 25 Perythons.

DWARF_FALL => Dwarf Falls
Save 13 barrelled dwarves.

EERIE_GARDENER => 1,2,3...Plant!
Grow 100 barbed vines!

ELDRITCH_DOOM => It's a kind of magic
Defeat 50 enemies with Eldritch Doom explosions.

FOLLOW_RABBIT => White rabbit
Scare 11 idle white rabbits!

FROZEN => Winter is coming
Freeze 100 enemies with the Sorcerer's Stones.

GARDEN_SONG => Garden Song
Activate 50 magical plants.

GARGAMEL => Gargamel
Squish 10 gnomes!

GATHERING_MAGIC => Gathering the magic
Defeat 80 enemies with the magic Blossoms.

GLOOMICIDE => Gloomicide
Defeat 100 gloomies before they duplicate.

GNOLLBUSTER => Gnollbuster
Defeat 900 gnolls.

GNOLLUM => Gnollum
Defeat 100 Bloodsydian Gnolls.

GREEN_ARROW => Green Arrow
Defeat 500 enemies with reinforcements' projectiles.

HEAVY_WEIGHT => Heavyweight Class
Stun 10 or more enemies with a single clobber.

HOLDING_OUT => I need a Hero
Complete 3 stages without the hero dying.

ITS_A_TRAP => It's a Trap!
Prevent Mactans from webbing at least 8 towers.

JAGGED_ALLIANCE => Brother vs brother
Have your Renegades defeat 50 twilight elves.

KILLER_TOMATOES => Killer Tomatoes!
Defeat 500 enemies with the poison Vines.

KILL_BOLJARK => The Banner Saga
Have Bolverk kill 100 enemies.

LAST_SERVICE => I meant the red wire
Have your soldiers avoid 50 blasting spell explosions.

LIGHTNING_CAST => 1.21 Gigawatts!
Cast 1210 lightning bolts.

MITCHELL_HEDGES => Mitchell-Hedges
Collect the 3 strange skulls.

NIMLOTH => Nimloth the Fair
Stun 200 enemies with the white trees' power.

NOPAINGAIN => No Pain, No Gain
Deal over 100,000 damage with Sylvan Curses.

NOT_TODAY => Not Today!
Complete 7 stages without the hero dying.

PEEKABOO => Peekaboo
Find the three playing friends.

PERFECT_PARRY => Footloose
Perfect Parry for a total of 1000 damage.

PEST_CONTROL => Pest Control
Kill 100 Mounted Avengers.

PHANTOMZONED => Phantom Zoned
Keep enemies out of time for a total of 1000 seconds.

SENTINEL => Red Five
Complete any stage with 5 active arcane sentinels.

SLUMBER_ARROWS => Lullaby!
Defeat 50 sleeping enemies.

SORCERERS_APPRENTICE => Sorcerer's Apprentice
Find the three apprentice relics!

VALAR_MORGHULIS => Valar Morghulis
Mark a total of 5 targets simultaneously.

VOLUNTEER_TRIBUTE => I volunteer as tribute
Deploy 500 or more reinforcements into battle.

VORPAL_BLADE => Vorpal Blade
Defeat 5 Bandersnatches only by dealing them damage.

WAR_NEVER_CHANGES => War never changes
Have 1,500 of your own soldiers defeated in battle.

WILDFIRE_HARVEST => Wildfire harvest
Throw 1,000 burning nuts.

These achievements had no counter, I suggest you don't modify its value.

HARD_MODE => Supreme Defender
Complete the Campaign in Veteran difficulty.

IMPOSSIBLE_MODE => Peerless Defender
Complete the Campaign in Impossible difficulty.

KILL_BALROG => The Pick of Destiny
Defeat Godieth the Dark Balrog.

BAG_OF_RICE => My Lord Bag of Rice
Defeat Baj'Nimen the hateful warlord.

FREEDOM_FIGHTER => Malik Unchained
Help Malik escape.

OFF_HEAD => Off with your head!
Defeat Bram the Beheader.

WILE => Wile E.
Help Wile E. capture the elusive bird.

ACE_SPADES => Ace of Spades
Complete Stage 5 without building any barracks.

BEANS => Fee-fi-fo-fum!
Grow the beanstalk to the clouds!

BRAVE_TAILOR => Brave Little Tailor
Don't let the hero die against an Ettin on Stage 4.

CANDY_RUSH => Candy Rush
Save Hans and Ethel.

DING_DING => Ding! Ding! Ding!
Raise all 3 basic heroes to level 10.

FORBIDDEN_RUINS => City of Splendors
Earn 3 stars on each Ancient City campaign stage.

GEORGE_FALL => George Fall
Find George!

GET_PARTY_STARTED => Get the party started
Win stage 1 with 3 stars.

GREAT_DEFENDER => Great Defender
Complete the Campaign in Normal difficulty.

GREAT_DEFENDER_HEROIC => Heroic Rush
Complete all campaign Heroic challenges.

GREAT_DEFENDER_IRON => Iron Rush
Complete all campaign Iron challenges.

KILLTACULAR => Killtacular!
Crimson Sentence 10 enemies in a single wave.

KINGSFOIL => Kingsfoil Leaves
Give regeneration 25 times to the same soldier.

LIGHTNING_KILL => Only counts as one
Defeat 10 enemies with a single thunderbolt power.

LIKE_TO_MOVE_IT => I like to move it!
Entertain the funny lemure.

MALICIA => Game of Thrones
Defeat Malicia!

ROBIN_OF_SHERWOOD => Robin Of Elfwood
Earn 3 stars on each Elven Woods campaign stage.

ROCKSTAR => Rockstar
Earn 50 stars.

SCISSOR_FINGER => Scissorfinger
Find the matching bushes.

SERIOUS => Why so serious?
Defeat Hi-Hi Enha, the Gnoll Chieftain.

SHEZI_BANZAI_ED => Shenzi, Banzai & Ed
End stage 3 without scaring more than 3 hyenas.

SIMCITY => Simcity
Build a Level 4 tower on every holder of a stage.

SIMON => Shroom Says
Complete a 9 tap challenge of the Shroom game.

STARDUST => Stardust
Earn 30 stars.

STARFIELD => Starcraft
Earn all stars from each Campaign stage.

STARGAZER => Stargazer
Earn 15 stars.

TINKERBELL => Pixiebell
Earn 3 stars on each Faery Grove campaign stage.

TRUTH_DARE => Truth or Dare
Call 13 or more early waves on any given stage.

WE_ARE_CHAMPIONS => We are the Champions
Defeat the Spider Goddess!

The heroes in save keys matched name.

hero_elves_archer => ERIDAN
hero_arivan => ARIVAN
hero_catha => CATHA
hero_regson => REG'SON
hero_elves_denas => PRINCE DENAS
hero_rag => RAZZ&RAGS
hero_bravebark => BRAVEBARK
hero_veznan => VEZ'NAN
hero_xin => XIN
hero_phoenix => PHOENIX
hero_durax => DURAX
hero_lynn => LYNN
hero_bruce => BRUCE
hero_lilith => LILITH
hero_wilbur => WILBUR
hero_faustus => FAUSTUS

Heroes level and XP
Lv 1 0
Lv 2 1300
Lv 3 5300
Lv 4 11300
Lv 5 19300
Lv 6 31800
Lv 7 46800
Lv 8 64300
Lv 9 88300
Lv 10 115300

Thanks to SteamDB
https://steamdb.info/app/816340/history/

PHP source code that I use to generate these data
https://gist.github.com/ve3/172a3ac5b8c957dab8f9dbee5f33058b

Heroes level and XP
https://steamhost.cn/steamcommunity_com/app/458710/discussions/0/360670708787507239/#comment_1845819570023842397