Just to clarify, an "attention whore" is a noun that can be used to describe a person (usually a woman, in fact, but the term can be used for men as well) that seeks attention, and would do almost anything to get it, as if addicted to it.
The only Japanese term I know that bears any similarity is かまってちゃん but it's not a negative thing. Also, かまってちゃん tends to seek attention of that special someone, which doesn't have to be the case for "attention whore". As the "whore" part suggests, there is no hint of loyalty or attachment in it. And in relation to comments: no, かまってちゃん is not negative per se. It is not uncommon for a Japanese girl to send a かまってちゃん sticker to her bf, which is used in the similar context as the "poking" functionality that existed on Facebook. It's their way of being cute.
I'm looking for a Japanese phrase that conveys attention-seeking and is at the same time not cute. Something nobody would want to be called.