the reference pad needs to overlap with your graphical elements. All graphical elements need to overlap each other.
So how to build your part
First draw your arc from multiple arcs and a line. I chose to have an outer radius of 3mm and a with of 0.6mm but a maximum corner radius of 0.1mm (arbitrary for demonstration purposes.)
This means my line thickness of the arcs can be 0.2mm and i need 3 arcs to fill the “pad”.
Place 3 arcs with center at (0, 0), angle = -180°, linethickness=0.2 and starting points at (2.9, 0), (2.7, 0), (2.5, 0) respectively. The layer you place them on is unimportant for now. (I used F.SilkS)
At the end you should have something looking like this:
Now also add a line connecting the endpoints of the inner and outer arcs. Linethicknes again 0.2mm (best done using the grid setup with 0.1mm for my measurements)
After that it looks like this:
Add a polygon with your desired linewidth and shape to form the sharp point. (I chose 0 linewidth to get a really sharp point)
place a rectangular smd pad somewhere inside the covered are where the sharp point meets the arc.
Select the pad plus the arcs and lines and the polygon, right click -> create pad from selected shapes. The result will look like this:
An alternative option is the use of freecad and kicad stepup. This allows you to create the pad shape in a parametric CAD program and export it as a pad to kicad. Kicad StepUp: The Sketcher for Footprint generation