I have heard people saying things like: "he is the Winningest person" or "I am the most Pleasingest person" etc...

The sentences they are used in aside, is it right to use ing+est on the end of the same word?
Hey Winger, welcome to the forums..

Hmm! noo - it sounds terribleEmotion: smile
haha. I agree it sounds terrible..and I am disgusted that it could be considered as being a word

However, I'm curious as to whether there is any rules of Grammar that would say that just shouldnt be?
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It's bad grammar.

Here's a quote that I think sums it up rather nicely:

"The best way to be certain whether the comparative and superlative forms of a particular adjective or adverb are formed by the -er/-est endings or by the words more/most is to consult a college dictionary. If there are no comparative and superlative forms listed with the endings, then that word takes more/most."

from the site: http://www.ucalgary.ca/UofC/eduweb/grammar/course/speech/1_4d.htm

I looked up "winning". It's listed as an adjective. The . Thus, it's bad grammer.

Words like "winningest" seem to come from lazy but creative native speakers, whom I suspect must have limited vocabularies and feel the need to invent words. Pick the right word(s) instead. Why not simply "most successful"?
One last thought.

A good dictionary lists all words. A word will either have its own entry or will be listed under its root.

If this is for a bet or you're trying to convince someone, ask them to find "winningest" anywhere in a dictionary.
the reason i asked was because i have seen the word used in various articles. I hate the word!
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I think that the answer to the question of whether it is right or not to use "ing" + "est" adjectives is to some extent a function of the level of language being employed. It's clearly wrong in "standard" English prose, and even in ordinary speech. But in certain types of writing that are trying to be colorful, I think it might be acceptable as part of a cute-sy turn of phrase. As though saying: "Look at me, I'm so clever, I can use this unusual form of the superlative." It may be annoying, and not the type of writing I'd ordinarily want to read, but I'd hesitate to say that it was always and everywhere flat-out wrong. As with a lot of these questions, it depends on context, even though there may not be very many contexts in which such a form should be acceptable. IMHO.
I was not trying to put anyone down with my comments, I was merely speculating about the origins of "winningest". By the way, I searched for "winningest" on google. My first page of results was nothing but sports related articles. Do sports commentators tend to invent words like this?

I venture to say that it is flat-out wrong. "Winningest" is not even as proper as "irregardless" or "ain't" -- words that can be found in reputable dictionaries.

"Winningest" is as much a word as "sdgklgjrw9svd".