I think I figured out how to build Supernatural Durability out of spare parts

[Bruno]

Mmph.

So. New version looks like this, costs 155 points (again, close to the RAW cost):

• Injury Tolerance: Unbreakable Bones (Accessibility, only at 0 HP or more, -20%; Cosmic: Can't be crippled at all, +300%) [38]
• Immunity to Pain [30]
• Immunity to Unconsciousness [30]
• Unkillable 1 (Achilles' Heel, Megadamage, -10%; Achilles' Heel, Something Occasional, -30%, Cosmic: Can keep going after -10xHP, +50%) [55]

I don't like pricing Cosmic: Can keep going after -10xHP as a simple Avoiding Drawbacks. That's not a Drawback of the advantage, that's a Drawback of being a character in GURPS. I went with it anyways, because +50% gives the metatrait a point total very close to the original advantage.

I'm open for lots of debate on the value of that enhancement. On the one hand, taking the Achilles' Heel limitations off makes the character functionally immortal, with infinite hit points. That seems like it should cost more than 75 points :P
On the other hand, the infinite hit-points are all on the far-negative end. Without taking the rest of the package, you are suffering big penalties or are unconscious, and will take a very long time to heal back up to a point where you don't pass out every time you try to do something. I'm not sure all those negative hit-points are worth, say, a +300% Godlike Tricks cosmic - it's not that good.