You are the most stupidest person on earth!
You are the most stupidest person on planet Earth.
9 Answers
I mean: until you don't take the English lessons here, which sure have a lesson on adjectives (comparatives and superlatives) we do not want to get into this issue any deeper, do we? 
Hmmm, wait, may be I should say: more deeper?? 
Well, under the circustances, I can only say:
Look who is talking!
Well, alexisstar12, what you have stated is not grammatically correct, and I don't exactly know what you are trying to say here, you might want to clarify so that we can answer your question.
So, to the other users who answered this question, I agree, this is quite hilarious in how it was stated. But, isn't this supposed to be a forum where we try to encourage people and help people and try to get them to keep visiting this site? Yet, somehow to me (maybe not others, but at least to me) making fun of a person and something that a person posted doesn't seem to go along with the overall theme of this site. After all, in the official rules and guidelines it says:
II. Be a positive part of the SpanishDict community
- Be helpful, nice, and polite. If someone's Spanish or English is incorrect, politely provide a correction. There is no need to humiliate or be sarcastic for any reason.
Yet what people have said don't seem to agree with this standard.
Just a thought 
You must be speaking about one of our U.S. Republican Senators or maybe you are talking about all of them? If you are talking about our total Congress than you must use the plural: They are the stupiest representatives on planet earth or you can say we have the stupidest Health Care on earth! Anyone of these have the correct grammar and truth. I would use instead of stupiest, I would use- the biggest brainless,halfwitted,and imbecilic US Congress known on planet Earth. In any language our Congress stinks and so does our Health Care! God Bless America the home of "drop dead in the street medical plans A, B, and C or part D". your pick!
What was the question?
I am not quite sure if you are asking for a translation or if you are making a statement. Either way, it is not a very kind thing to say.
Maybe you could come up with a more constructive way to make your point and we would be happy to translate. 
Is it possible this person was asking for a translation of the phrase? That would have been my assumption. However, I'm choosing not to translate it.
Are you talking about Bush? 
Well, "this person" just turned 13, according to her profile. Perhaps that's relevant somehow, because from my experience with that age, such expressions are fairly common.
Indeed, kids that age often use insults to express affection.
Ok now hold on there just a second.
You can't say "most stupidest."
So...that kind of looks bad there when you sit there calling us stupid...Just saying....
