To make my question clear I've added a picture above which I drew myself which shows 2 scenarios where the only difference is the sign of the charge. Essentially we have an electric field produced by a positive electric plate and it's effects of repulsion/attraction on a positive/negative charge.
Now, to calculate the voltage I simply use the Voltage=Delta Energy/Coulomb formula. I use the Lower potential energy point as the reference point.In the positive charge scenario it gives me +12V (This makes sense as it's at a higher potential energy point relative to the reference point). Whereas the negative charge scenario it gives me -12V (which doesn't make sense since it's at a higher potential energy point RELATIVE to the reference point so it should also be positive).
Do we just take the absolute value of the charge when dealing with Voltage? I hope I explained it well enough. I'd really appreciate some help. (The numbers are arbitrary by the way)