I think this works for all characters, since we all end up punching ukumari. You need to get sanctuary as it does damage to enemies near you after you use a potion and allows you to clear ukumari without having to go through an extra wave. This also works with runapuma when you have to hit the orbs. There is a downside, since you need to use a potion to activate it, you need to be below full health and getting hit usually costs time.

You can see how I did it for reference once my new run goes through.

That's a cool find! I'd really like to see it in action, because I didn't know that Sanctuary dealt that much damage. (My runs are still going through, so I'll be patient and wait to see yours.)

If this is that great an effect, then I can make a save that uses this as its last spiritual core.

It does a surprising amount of damage which has made dealing with ukumari so much easier, now I can rage less XD.