It has its merits, namely the combat rules were really well developed compared to other editions. If you like tactical RPGs (I do), 4e played like that during combat.
What people hated (especially longtime players) was the shift in focus away from role-playing in published materials. I mean, that doesn't really change anything but it leaves everything up to the DM and players, so new players aren't going to know that. Also the published materials really really omitted a lot of setting detail that was in previous editions, some of the sourcebooks were just a waste of money.
Also the Essentials line was released later on which felt a lot like 3.5e (except unnecessary) nickle and diming to people. In reality they were not, they just added more character options in a way that was easy to understand for newbies.
I started playing a short time before Essentials came out so I was able to get a good perspective on before and after.
Not sure if you're referring to a specific line in something, but
殺人 Satsujin is a kango way of writing murder
殺人鬼 Satsujinki = heinous murderer, basically. Serial killer, really horrifying murders, that sort of thing. Hannibal Lecter would be satsujinki.
Nasu did a wordplay on the latter to work part of Shiki's name in.