La Tenia didn't attack Alex because she was so damn sexual and beautiful, but because he hated her and what she represented, and that's the reason behind most crimes. Not money, not sex, but pure hate and a feeling of superiority.
Most movies will portray violence as a poetic thing, even the most intelligent ones. Think about Taxi Driver, one of the most crude films ever. It's violence has style and looks cool, although it's not, and it's very real. The same goes for American History X. In Irreversible, violence is not a camera looking for a cool angle in a fight, a la Fight Club, but a smell, a scream, a glimpse of something horrible that is still there when you're so stupid to dare to open your eyes. There's no escape once hell breaks loose, and you can't go to hide under your mother's skirt and wait until it's gone. Nooo, it will go after you like a rabid dog, and you will suffer.