Here is the full list of all 71 Heart&Slash achievements.
DEFEAT THE GUARDIAN
REACH FIFTEEN HEARTS OF MAX HEALTH
DEFEAT YOUR FIRST C.O.P.S. FLASHBANG
DEFEAT YOUR FIRST MAGNET
FINISH A LEVEL UNSCATHED
CLEAN THE REMNANTS
DEFEAT FIVE TRIPODS
DEFEAT TWENTY FIVE ARMOURED ENEMIES
SURVIVE FIFTY ARENAS
DEFEAT ONE HUNDRED BIGGRUNTS
BEAT THE UNBEATABLE
DEFEAT ONE HUNDRED SMALLBOTS
DEFEAT TWENTY FIVE LASER ARMED ENEMIES
DEFEAT FIFTY ELITE ENEMIES
EQUIP YOURSELF COMPLETELY
DEFEAT FIFTY SHIELDED ENEMIES
HAVE YOUR ENEMIES DEFEAT TWENTY OF THEIR OWN
DEFEAT ONE HUNDRED FLYBOTS
DEFEAT TWENTY FIVE BIGGRUNTS
SURVIVE THE DOCTOR'S CHALLENGE
DEFEAT TWENTY FIVE NIMBLEBOTS
SURVIVE SLASH'S CHALLENGE
SURVIVE TEN ARENAS
EXPLORE ONE HUNDRED ROOMS
JUMP A THOUSAND TIMES
DON'T BE MEAN
DEFEAT TWENTY FIVE SMALLBOTS
DEFEAT TEN LASER ARMED ENEMIES
DEFEAT YOUR FIRST TRIPOD
DEFEAT TEN NIMBLEBOTS
DEFEAT TEN BIGGRUNTS
DEFEAT TWENTY FIVE FLYBOTS
DEFEAT TEN SMALLBOTS
SURVIVE FOR TWENTY MINUTES
DEFEAT TEN FLYBOTS
UPGRADE A WEAPON AND LET THE GOOD DOCTOR KNOW
DEFEAT YOUR FIRST SHIELDED ENEMY
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
LONG LIVE THE QUEEN
DISRESPECT THE AUTHORITY
DEFEAT ALL BOSSSES IN THE FACTORY AND THE CITY
CREATURE OF THE NIGHT!
UNLOCK ALL BLADES
DEFEAT TWENTY OF EACH DOG'S PARTS
DEFEAT FIFTY ARMOURED ENEMIES
DEFEAT TWENTY FIVE SMALLBOTS IN THE CITY
DEFEAT ONE HUNDRED NIMBLEBOTS
DEFEAT TWENTY FIVE TRIPODS
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 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
UNLOCK ALL AXES
BAT FIFTY MISSILES
BEAT QUASSY WITH A FULLY UPGRADED RUBBER DUCK
UNLOCK ALL FIST BASED WEAPONS
BEAT QUASSY WITH THE PROTOTYPE