Which boss soul in Demon's Souls (2009) was the most satisfying to claim?

Vessel of Souls
Demon's Souls (2009)
Soulsborne
Games
Vessel of Souls poll options
Vessel of Souls
Demon's Souls (2009)
Soulsborne
- Maiden Astraea's Pureblood Soul
- Old Monk's Yellow Demon's Soul
- Dragon God's Dragon Demon's Soul
- Old Hero's Hero Demon's Soul