Maybe this is different here in Europe, but HR's role is to protect the company. HR in my experience does not do whatever a manager wants. Let's say you have a toxic direct, unless you have a 50 page document outlining every single transgression or bad behavior and the steps you took to mediate said behaviour, including corrective feedback, and statements by the toxic employee's peers supporting your observations, HR will often times do exactly nothing and happily ignore you, and even then, they could still propose "mediation" or "conflict resolution" procedures because they are afraid of an unfair dismissal law suit or whatever.