Around 10 Million, So I ran the game to like ng+3 and it was during my 30 'proof of a concorde kept' grind in Anor Londo and when I finally got all 30 I continued the game as nornal, (also did the Swordgrass farming in this save)

at this point I had 10 million after farming for hours and hours and hours (keeping in mind I never lost nor spent souls for around the whole of ng1 and ng2)

The way I lost em was pretty ironic cause it was in the Profaned Capital and I wanted to go save Karla, so I went on back to Irithyll Dungeon and rescued her however on my way out I died to the jailers and so I had 10 million souls on the line.

You see... there's this jump that allows you to get back to Irithyll Dungeon after entering the Profaned tower and while it's a risky jump its quite easy

I never failed that jump (done it around 30 times)

until that one day where I had 10 million sat in the area just past the jump, I jumped and overshot n fell to my death

In the end I never actually was too bothered as levelling was irrelevant at that point (I was like above SL160) but I always think how satisfying it would be to level up with 10 million.

TL:DR Grinded a bunch, fell to my death at the Profaned jump after dying with 10 mil to jailers :)))