noun
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?).
彼はまるで何様かのように振る舞っている。
He acts as if he were some kind of big shot.
「何様のつもり？」と彼女は怒って言った。
"Who do you think you are?" she said angrily.
adverb
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.
何様、彼がそんなことをするはずがない。
There is absolutely no way he would do such a thing.
何様、私が諦めるものか。
I certainly won't give up.
何様 is more pointed and sarcastic than 誰, often implying the person is acting above their station.
絶対に is the common modern adverb for 'absolutely'; 何様 is a literary, emphatic alternative.
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'.