Massacred him and removed his ability to ignore it. Rage Beyond Death is gone, the level 14 feature is now Rage of the Gods:

When you activate your Rage, you can assume the form of a divine warrior. This form lasts for 1 minute or until you drop to 0 Hit Points. Once you use this feature, you can't do so again until you finish a Long Rest.

While in this form, you gain the benefits below.

Flight. You have a Fly Speed equal to your Speed and can hover.

Resistance. You have Resistance to Necrotic, Psychic, and Radiant damage.

Revivification. When a creature within 30 feet of you would drop to 0 Hit Points, you can take a Reaction to expend a use of your Rage to instead change the target's Hit Points to a number equal to your Barbarian level.

They did make the base class level 11 feature Relentless Rage better, it now restores you to double your level of HP instead of 1 HP if the save succeeds. Zealot Barb also lost its level 3 ability that let them be revived without the caster needing spell components and instead gets a pool of d12s to heal themself with.