[Q] Need only root topic

I may be stupid or just quite how, but I can not find what I want.

Only the root.
I need only rooting for nothing else than away win with preinstalled software for example. Mcafee. etc., etc.
None of what I have tried here does not work.
IOroot no work
Towelroot no work
Purple Drake no work
stump Root no work
RootTool no work

My phone is the LG-D855 32GB
Android 5.0 version of the software V20e-EUR-XX

Can someone tell me what 100% works?

Such a wire-frame model, I am old and slow-witted man and use google translating.