Forgot unlock-pattern of android device without registered Google account. Will factory reset work? I want to access a Samsung S6 Edge that I haven't used for a long time, 
so I don't care about any data on the device.
I forgot the unlock-pattern and PIN but I never registered any Google-Account on it.

What happens if I do a factory reset? Will there be a prompt for a Google account even if there never was one registered on the phone before? Because I don't want to get stuck on that prompt.

Or will the reset go through without any further security issues?

Or is there even a better way to access the device?
A factory reset will work for this issue. But you may lost your data.

I repeat you may loss because some cyanogen device didnot delete all data in a factory reset(including my device).

So try it.