Is there a word for someone who holds a position but they have no real power, they just merely have the title but not the power or privileges that come with it? I'm looking for a word with a negative connotation, almost like a placeholder position.
In general, figurehead seems like the best fit to me. From Oxford Advanced Learner's Dictionary:
figurehead: a person who is in a high position in a country or an organization but who has no real power or authority
However, in some cases this is more of a built-in feature of the position rather than of the individual holding it.
In terms of connotation, "figurehead" seems fairly neutral to me. It doesn't really have a positive connotation, since it implies a large degree of powerlessness, but I also wouldn't say it's necessarily negative.
Here are some other questions on the site that discuss the concept of a figurehead, and also the complementary concept of the "power behind the throne":
Here are some ideas.
Vice-presidency (noun) (for example, "The position of such-and-so is as meaningless as the U.S. vice-presidency")
Puppet president (or whatever position you're talking about)
Token (for example, if a woman is promoted to vice president of something, but no one listens to her point of view, she may start to suspect she was hired as the token woman, i.e. she's just a token)
Mock (adjective) (for example, mock-ministers -- see http://prelude-mag.com/2013117fjtog2vngjasdrjesxvbzxk0avk7k3/)
Titular (adjective): existing or being such in title only; nominal; having the title but none of the associated duties, powers, etc. (dictionary.com)
As already proposed, figurehead is very good.
I'm not sure if this fits your bill, but since you mentioned "placeholder", which has the implication of something or someone being temporarily used to hold a position while a more worthy replacement can be found (or put into power), I would like to suggest chair warmer.
noun, Informal. 1. an officeholder, employee, or the like, who accomplishes little, especially a person who holds an interim position.