Agony
Wendell was accustomed to pain; in fact, he often got off on it. The excitement that stirred itself low in his gut each time he had placed himself in a potentially dangerous situation, each time he confronted possible death or injury and fought to make himself victor, the one inflicting greater injury than he himself received, only fed his adrenaline, only drove him into behaving with more aggression, more recklessness, more violent enthusiasm in the next similar circumstances to come along. With his twin sister he would revel in causing and receiving injury, the sight and smell of his own and others' blood becoming an intoxicating aphrodisiac, only further spurring him on. Pain and pleasure were tantalizingly entwined for him, making their private times together that much more entertaining when they got creative.
Wendell could tolerate a high level of physical pain and thrive upon it. Even now, with his face split bleeding heavily, his teeth loosened, his head throbbing steadily, and his inability to sit up, let alone to stand, due to the concussion caused by having his face slammed repeatedly into the floor, he could have rode it out as simply a greater challenge than usual to endure.
But to have this physical pain was nothing compared to his knowledge that his twin sister, his Darlene, had been taken from him, and could not escape, could not force her way back to him. To sit slumped on the floor, his own blood slowly seeping out of him, and to listen to hear screams, to vividly picture in his dizzied mind exactly how she was being violated and to know that he could not stand, let alone go to her and keep her safe, rip into those assaulting her and derive vicious satisfaction from making her screams become theirs…to sit there with his stomach churning, his own breathing harsh and staggered to his ears, and know himself to be utterly helpless to stop his sister's rape was the greatest pain Wendell had ever experienced, beyond any physical pain possible for him to have born.