........no, it's made fairly obvious he was always into the Dark Arts and his potions book shows he was always fairly clever and had a mind that liked to work things out and improve things. If he designed it because of the Mauraders, why never use it on them? And it's also stated Snape invented the 'hang you from your ankle' spell, so he must have been the one to start using it on people (if that's what your sexually assaulted bit is aimed at, so he's the one who was 'sexually assaulting' people first). Snape was no saint at school. And even if he was harassed just for existing by a bunch of griffydors, well, he was in another house, and it's still hardly an excuse to invent spells that can cause multiple slash wounds to people and kill them in short order unless there are people near by who know how to heal magical wounds and deal with blood loss.