I was curious what the least possible points total was, but keeping Wall out makes the challenge actually interesting.

Someone in our Discord (Avorian, shoutout) came up with this. Given the Wall ban, if you replace Sauna with Marauder, this is most likely optimal, though I have not calculated the negative score possible (will be somewhat dependent on player count to determine curse pile and silver/gold supply, also questionable whether or not you could add Platinum):

To show my work: the strategy is to drain golds/silvers and then end game by piling knights/golds/silvers/curses somewhere down the road. Young witch is basically a free slot so of course you include it. Shelters and platinum likewise. From there we get into maximising number of uniques coming from kingdom.

The gold standard is producing >2 uniques in a kingdom pile. There are plenty of split-piles, heirloom piles, and piles with other set up to get at least two from every kingdom slot. So lets see who wins:

1. Knights produces a whopping 10 uniques with a 2vp downside from Josephine, so 9 + 1/3 effective uniques.

2. Marauder brings ruins and spoils into play for 7 uniques.

3. Tournament brings 6 uniques (note: trash province with anna)

4./5. Peasant and page each bring 5 uniques.

6. Exorcist brings 4 uniques (note that ghost is always brought by an unrecoverable treasure and you cant waste a slot on masq, and the kingdom pile with it is only 1/3 of a unique effectively)

7. Leprechaun brings 2 uniques (wish, again otherwise have to trash something unrecoverable) and can give you twice miserable.

8./9. lurker and necromancer bring in 5 total uniques for an average of 2.5

As far as I can remember, no other card brings in more than 3 uniques not already covered (except castles, which counters itself with VP). So add in a 2 unique pile of choice.

In total the 10 cards from kingdom and associated setup gives 10 + 7 + 6 + 5 + 5 + 4 + 2 + 5 + 2= 46 uniques, and copper/estate/YW/shelters bring us to 52. So thats -156 points. Twice miserable, josephine and estate points bring it to -157.

Then you have -150 from all curses/golds/silvers (assuming 2 player).

So in summary I get -307 without plat, -310 with it.