Reborn race (5e)+ Hollow one supernatural gift(5e) + 5.5E barbarian

This might be the most hardest to kill build ever 

For those that only have the 2024 PHB, can you explain the other parts of the title and why so hard to kill?

Reborn is a zombie race. The feature that matters for this is that they get advantage on death saves. Hollow one always you to regain 1 hp when you roll 16+. With the ungodly tanky-ness of a 2024 zealot barbarian even with your enemy can drop you, the dm has to target you with an attack to get you to fail a save. And you get back up 25% of the time with out advantage. It’s like 45% that you stand up with advantage. So yeah…

I’m talk mostly in general about barbarians tank power and most people consider critical roll official. It’s also in explores guide to wildmount is official. It is written and the cover features that are on all official books appear on EGW. But Wagnarokkr covers it very well and very analytically.