I dunno, depends on how large a knife i have and how much time, a couple of hours worth of slashing should do the job.... but seriously, that guy must have serious issues, i could never bring myself to harm something that is no threat to me, much less injure cats and watch them get torn apart and he seems to enjoy it. IMO they should put him away for good, coz doing that to cats is one step away from doing it to kids. Its like the Saw (the movie) for animals.