Lucius the Eternal is jokingly considered the ultimate rapist by the fandom. Although he's actually a masochistic swordsman, the fact that he serves Slaanesh sort of turns him into this trope. He will penetrate the rear armour of anything with his Rod Lash of Torment. OH YEAH!!
On the subject of Slaanesh, Daemonettes have been depicted as raping (or being raped by) almost everyone in the setting at least once. Being daemonic servants of the literal god of perversion and depravity doesn't hurt.
Any and all Dark Eldar are subject to this treatment, and although they are known to rape on occasion they much prefer to torture their victim to death, resurrect them, torture them again and then eat their souls. However, since torture is basically sex for them...
Folca (a minor daemonic harbinger from Pathfinder) has dominion over "abduction, strangers, and sweets," and his favorite weapon is the net. Certain dark corners of the fandom consider him Golarion's Pedobear.