Tafsir of Qaf 50:12

"The people of Noah denied before them..."

He intended by "Pharaoh" his people, just as in the Almighty’s saying: {from Pharaoh and his chiefs} (Yunus: 83).

This is because the noun to which the others are conjoined is "the people of Noah," and the conjoined entities are groups. Regarding {all}, it is permissible to intend by it every individual among them, or to intend all of them collectively. However, he singularized the pronoun referring back to it based on the grammatical form (lafz) rather than the meaning (ma'na).

{...so My threat was realized}

Meaning: My threat became necessary and descended, which is the word of punishment. In this, there is consolation for the Messenger of Allah (peace be upon him) and a threat to them.

{Were We exhausted by the first creation?}