In Dark Souls II, whenever you die, your character's Hollowing progresses a little more, reducing your Max Health slightly. However, I am unsure how far the Hollowing can progress, whether to a point of complete Hollowed or a limit on the Health reduction. Does anyone know?
According to user @somebody (comments of the question) and to that source:
This will continue until it caps at 50% of maximum HP, unless the player has a sin level of wretch, which it will cap at 95%.
As stated by Bart W in the comments, there is a ring that caps the HP loss, according to the wiki:
[...] stops HP reduction at 80% instead of 50%.