Here's a build I made:
https://underrail.info/build/?HgsDAwoIBwQAwqAAAAAAAABpZAAAwqDCoChzwqAAAAAAAMKgeF8IRDvDnRXDnybDoR_DnmNVYsKyccKn4p-iA-KrhgXiv4cF4r-aAt-8At 20% (236 without armor/juggernaut) hp it will have resists:
Mechanical: 62% (15 from heavy metal, 17 from conditioning, 30 from stoicism)
Heat: 47% (17 from conditioning, 30 from stoicism)
Cold: 47% (17 from conditioning, 30 from stoicism)
Electricity: 60% (30 from tempered and 30 from stoicism)
Everything else is 30% from stoicism
With Aegis, Morphine and Nervosomnifer:
Mechanical: 187%
Heat: 172%
Cold: 172%
Electricity: 185%
Everything else is 155%
Also food can give from 5% to 35% resistance to 1 element, and Parafibrotic Regenerative Injection gives 15% to mechanical and heat.
I don't know what is max resist but I assume it's 95% like armor penalty. So at 20% (236) hp without armor you can survive up to 4720 damage with meds.
Without meds:
621 of mechanial damage
445 of cold and heat damage
590 of electrical damage
337 of every other damage
With heavy armor and juggernaut these numbers will be even higher.