[Gwathagor]

I believe both Barad-dur and Mt. Doom were located on Gorgoroth. If the plateau wasn't violent itself, it certainly contained great violence, being both an unstable, volcanically active area and the lair of a demonic supervillain who is arguably responsible for most of the violence that occurred in Middle-earth.

I would also argue that Beorn is considerably more violent than Eol on pretty much all levels. Higher kill count. Uses claws and fangs, rather than poison darts. Impales victims remains on front gate. Is essentially part wild animal. And I can't imagine that transformation being particularly peaceful either...