Here is the full list of all 40 Dead achievements.
Only use explosions when killing Dying Ember
Kill Dying Ember on Easy Mode
Complete DEAD in Easy Mode
Complete DEAD with Boss Rush Mode and One Hit Mode enabled
Complete DEAD with Easy Mode, Boss Rush Mode and One Hit Mode enabled
Kill Eight Bears in Easy Mode
Never fire a bullet or explode when fighting Totem
Ring the bell
Kill Dying Ember
Never take damage from the clock
Dead
Kill Scourge
Kill Scourge without exploding
Do not destroy any crystals
Kill Glass Master
Never take damage when fighting Glass Master
Never dodge when fighting Glass Master
Kill Eight Bears using only explosions
Kill Migraine
Never take damage when fighting Migraine
Summon the second ring
Never allow Smelter to get the sword
Kill Furnace
Never dodge when fighting Furnace and Smelter
Kill Eight Bears
Kill Vescile
Never allow Vesicle to heal
Kill Vesicle without leaving the bridge
Kill The Silenced
Kill The Silenced within 60 seconds
Kill The Silenced before killing Migraine
Kill Totem
Do not dodge when fighting Totem
Kill Puppeteer
Do not dodge when fighting Puppeteer
Kill Eremite and Spectre
Kill Eremite first
Kill Progenitor
Kill Progenitor without exploding
Kill Progenitor without moving