The picture shows the stump. We ground up the main stump, but there are parts of it and the root under a block wall/fence dividing my property and my neighbor's property. We suspect that this is pushing the block wall and causing it to lean. (I show a men's size 8 shoe in picture for scale).
I'm able to dig under the root/stump a bit.
What is the best way to remove this and any other remaining roots under the wall.
update Added note that the wall is actually a block wall fence separating my property and my neighbors property. We suspect the root is causing the wall to lean towards his property. We hope to correct the lean once the stump is gone.