I was looking at classes and subclasses, and saw the Path of the Zealot barbarian, and the question if it could become almost immortal came to mind. At level 14, the Path of the Zealot gains the following feature:
Rage Beyond Death Beginning at 14th level, the divine power that fuels your rage allows you to shrug off fatal blows. While you're raging, having 0 hit points doesn’t knock you unconscious. You still must make death saving throws, and you suffer the normal effects of taking damage while at 0 hit points. However, if you would die due to failing death saving throws, you don’t die until your rage ends, and you die then only if you still have 0 hit points.
Combined with the normal barbarian feature at level 15:
Persistent Rage Beginning at 15th level, your rage is so fierce that it ends early only if you fall unconscious or if you choose to end it.
Could a level 15 Zealot barbarian just fight the Tarrasque by itself and live?