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