Revenge is pleasurable on a biological level, too. In studies, when people perform retaliatory acts of aggression, there is activity in brain regions associated with reward. However, the satisfaction is short-lived.
This stuff is 100% unrealistic. Everyone here (I mainly assume minors) who just loves fawning over violence without honor or humanity has to understand that. there aren't villains like Okaya and Johan Liebert that just smile at you once, show you one piece of evidence, and then boom you're their slave to torture/abuse. that doesn't happen. you can't get shot multiple times with a crossbow, lacerated multiple times on your tendons, literally exploded and shot full of shrapnel, and then chainsawed like you're a nu-metal fan. none of the human biology works like that. chainsaws don't even work like that. the moment she touched the fabric of his boxers, the fabric would've been caught in the chain, pulling the entire chainsaw into his chest cavity, most likely getting stuck on guts/bone.
Another way to think about (if you enjoy the literary elements of the work and not just the violence and art, or if you like religion) is to think about the symbology of the protagonist, Maria. She has been symbolized as "Holy Mother Mary" numerous times, so that means it's safe to assume her son symbolizes Jesus. When he was born, all he did was cry and Maria correctly assumed that he was getting it all out as early as possible (again, that doesn't happen). Her son was essentially preparing to bear the sins of humanity and all that crap and was crucified. Maria then goes off for all the torture you all seem to positively enjoy...
Whether you're religious or not, do you think the Jesus who lived on our planet would've wanted his mother to act as Maria did? Would you want your parents to obsess over your death, committing inhumane acts... instead of becoming truly strong and moving on, staying true to that same person you knew them as...?