On DesktopGL line primitives are nice and clean.
While on DirectX lines look jagged and dirty.
Even straight lines sometimes have 2px wdth.
Is there a way to fix this?
Well the two pixel line issue will be because you are using floating point positions, a line drawn at x = 1.5 will end up fat
I would try looking at your settings on the graphics device. Is multisampling enabled et al
Is this spritebatch or a draw primitives.
Either way i suppose it doesn’t matter.
Round your floats to integer amounts set your size to a integer amount.
Sampler state to point or point clamp (the clamp part doesn’t really matter for this either way).