important person; someone (sarcastic)
Often used sarcastically or in rhetorical questions to belittle someone's self-importance, as in 何様のつもり？ (Who do you think you are?).
Who do you think you are?
He acts as if he were some kind of big shot.
"Who do you think you are?" she said angrily.
absolutely; certainly; to be sure
Adverbial use, often in the pattern 何様…ない or 何様…まい, expressing strong certainty or determination. Somewhat literary or old-fashioned.
There is absolutely no way he would do such a thing.
I certainly won't give up.
Taking that attitude—just who do you think you are?
絶対に is the everyday adverb for 'absolutely', while 何様 in this sense is a literary, old-fashioned way of expressing the same certainty.
Standard kanji spelling; the reading なにさま is unambiguous.
Mixed kanji-kana spelling, sometimes used for clarity or emphasis.
Compound of 何 (what) + 様 (honorific suffix, state). The sarcastic noun sense likely developed from rhetorical questions about someone's status. The adverbial sense is an extension of the idea of 'in any case' or 'whatever the situation'.