LightningChart Support Forums

When the last X value in an X array is set to infinity, the effect is reversed

Infinity is slippery thing. Don't use it unless you sure it is supported and do things as you intended.
Is it just report, is it problem description? Are there particular reasons why x-point should be at infinity?

Because this graph can be moved, for our purposes there is a point in theory where the Y value is fixed no matter what the X value is，So the last point is going to be positive infinity

Concept of Infinity is important in Algebra, but for numerical analysis done with computer it is dangerous path. Unless mathematical software package is design to deal with infinity, it is very likely source of the problems. Either you run get overflow error or just strange results.
Keep your last points at XAxis.Maximum (or some finite value you not going to overcome). If needed, you can use Axis.RangeChanged event to update last points coordinates.

Even if you don't use infinity, using Double. Maxvalue has the same problem