Here is the full list of all 71 Heart&Slash achievements.
TOGETHER WE RISE
LONG LIVE THE QUEEN
DEFEAT ALL BOSSSES IN THE FACTORY AND THE CITY
DEFEAT TEN WORMS
DEFEAT YOUR FIRST MAGNET
DEFEAT ONE OF EACH ENEMY CARRYING A BLADE OR A SAW
UNLOCK ALL BLADES
CLEAN THE REMNANTS
SIDE WITH SLASH IN THE FIGHT AGAINST QUASSY
DEFEAT FIFTY ARMOURED ENEMIES
DEFEAT FIFTY SMALLBOTS WITH A BACKPACK
BEAT THE UNBEATABLE
BEAT QUASSY AND UNCOVER THE TRUTH
DEFEAT TWENTY FIVE TRIPODS
DISRESPECT THE AUTHORITY
DEFEAT TWENTY FIVE SMALLBOTS IN THE CITY
DISPLAY YOUR COMMITMENT
UNLOCK ALL AXES
DEFEAT ONE HUNDRED SCAVENGERS
DEFEAT TWENTY FIVE ENEMIES WITH A BACKSTAB
DEFEAT FIFTY C.O.P.S. ENEMIES
DEFEAT YOUR FIRST C.O.P.S. FLASHBANG
FIND SLASH IN THE OUTSIDE WORLD
UNLOCK ALL FIST BASED WEAPONS
COMPLETE ALL THE QUESTS IN THE FACTORY
HELP SLASH EXIT THE FACTORY
USE YOUR HEAD AND SAVE SLASH
BAT FIFTY MISSILES
SURVIVE FIFTY ARENAS
DEFEAT ONE HUNDRED BIGGRUNTS
DEFEAT FIFTY ELITE ENEMIES
DEFEAT ONE HUNDRED SMALLBOTS
DEFEAT THE GUARDIAN
DEFEAT TWENTY FIVE ARMOURED ENEMIES
DEFEAT TWENTY FIVE LASER ARMED ENEMIES
DEFEAT FIVE TRIPODS
REACH FIFTEEN HEARTS OF MAX HEALTH
DEFEAT ONE HUNDRED NIMBLEBOTS
JUMP A THOUSAND TIMES
DEFEAT FIFTY SHIELDED ENEMIES
HAVE YOUR ENEMIES DEFEAT TWENTY OF THEIR OWN
DEFEAT TEN LASER ARMED ENEMIES
DEFEAT ONE HUNDRED FLYBOTS
EXPLORE ONE HUNDRED ROOMS
SURVIVE SLASH'S CHALLENGE
DEFEAT TWENTY FIVE BIGGRUNTS
DEFEAT TWENTY FIVE SMALLBOTS
DON'T BE MEAN
SURVIVE TEN ARENAS
DEFEAT YOUR FIRST TRIPOD
DEFEAT TWENTY FIVE NIMBLEBOTS
SURVIVE THE DOCTOR'S CHALLENGE
SURVIVE FOR TWENTY MINUTES
DEFEAT TEN NIMBLEBOTS
DEFEAT TWENTY FIVE FLYBOTS
DEFEAT TEN SMALLBOTS
DEFEAT YOUR FIRST SHIELDED ENEMY
DEFEAT TEN FLYBOTS
DEFEAT TEN BIGGRUNTS
UPGRADE A WEAPON AND LET THE GOOD DOCTOR KNOW
CREATURE OF THE NIGHT!
DEFEAT TWENTY OF EACH DOG'S PARTS
DEFEAT FIFTY LASER ARMED ENEMIES
DEFEAT TWENTY FIVE WORMS
DEFEAT FIFTY WORMS
DEFEAT FIFTY SMALLBOTS WITH A FIRE BACKPACK
DEFEAT FIFTY SMALLBOTS WITH A FREEZER BACKPACK
FINISH A LEVEL UNSCATHED
EQUIP YOURSELF COMPLETELY
BEAT QUASSY WITH A FULLY UPGRADED RUBBER DUCK
BEAT QUASSY WITH THE PROTOTYPE