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