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