Say you have a straight line that is composed of 4 verts. is there a way to delete the 2 verts in the middle of the line and just have 2 verts on the ends? i guess you could call it “unsubdividing” Any idea? Thanks.
Select the two middle verts and then one of the end ones and Alt-m and select merge to last.
If it is for a larger mesh then Script>mesh>Poly Reducer can be useful.
you can merge them- select them in a row and merge at last.
is poly reducer bundled with blender / do you need python installed to run it?
give it a try 
Yes it’s bundled, you shouldn’t need python.
For small stuff, merging the verts manually is way better.