Death

Death was the cessation of life.

The Ninth Doctor told Rose that "everything dies". (TV: The Parting of the Ways)

The personification of Death, like Time and Pain, was an Eternal.

Alternate timelines
In one alternate timeline, the Doctor died during the time war with the Enemy and his body was auctioned on 21st century Earth for its biodata. (PROSE: Alien Bodies)

In another, he died and was buried on Trenzalore. (TV: The Name of the Doctor)