I think as far as gentlest I'd say the Alana Rose scene was disappointingly gentle. In hindsight, it was obvious he wouldn't be going all out on her, but the possibilities made me so horny I set myself up for disappointment there.
For roughest, it's hard to gauge. I don't watch every scene so I don't have the best sample size.
The two most recent Isabel Moon scenes got to uncomfortable levels for me. Usually you can tell when there's a cut due to reaching a boundary, or even if something "extreme" happens, the woman laughs or smiles and then carries on with exaggerated acted complaints or nothing verbal. With the recent Isabel Moon scenes, she seems reluctant to continue.
The other rough scene I can think of is the Vile Vixen scene.