Is there a way to align multiple vertices to another vertex? I need to align some vertices up with the vertices that is extending out the furthest on the X axis. I want to know if there is a way to make them all aligned in one step. Instead of messing with each vertices X position. Is there a way to do that?
Set pivot point to 'active element' and transformation orientation to 'normal'.
Duplicate the edge you want them to be parallel to, move it with G and Z twice (along normal) and extrude it (E+Z) to create a clear normal.
Select your unstraight edge and afterwards the created polygon, so the polygon is the active element.
Hit S to scale, Z twice and move the mouse or just press 0 to make it completely straight. 
Delete the temporary polygon.




Works always, no matter how your object is weirdly rotated in 3D space.