~っこない
There is no chance it will happen
You’ll be able to strongly dismiss a possibility in casual conversation.

こんなに広い川、跳んで渡れっこないよ!
konna ni hiroi kawa, tonde watarekkonai yo!
What do you think this sentence means?
There is no way I can jump across such a wide river!
Strongly dismiss an impossible outcome
~っこない is a casual conversational pattern attached to the verb stem to express firm conviction that something is completely impossible ("there's no way that...", "definitely can't...").
こんなに長い本、一日で読めっこない。
konna ni nagai hon, ichinichi de yomekkonai.
There's no way I can read such a long book in one day.
そんな話、誰も信じっこないよ。
sonna hanashi, dare mo shinjikkonai yo.
Nobody is ever going to believe a story like that.
Attach っこない to the masu-stem
Drop ます from the polite verb form and attach っこない. It is predominantly used in spoken, informal contexts.
今から走ったって、次の電車に間に合いっこない。
ima kara hashittatte, tsugi no densha ni maniaikkonai.
Even if we run now, there is no way we can catch the next train.
~はずがない vs ~っこない
Both say something is impossible. ~はずがない is neutral and fine in writing. ~っこない is casual and strongly emotional, used only in conversation.
~はずがない, there is no way (neutral)
一日で終わるはずがない。
ichinichi de owaru hazu ga nai.
There's no way it will be finished in one day.
Calm; fine in writing.
~っこない, no way! (casual)
一日で終わりっこないよ。
ichinichi de owarikkonai yo.
No way it'll be finished in one day!
Casual and emphatic; speech only.
「この荷物、一人で運べる?」「こんなに重いの、運べっこないよ。」
"kono nimotsu, hitori de hakoberu?" "konna ni omoi no, hakobekkonai yo."
"Can you carry this luggage by yourself?" "Something this heavy? There’s no way I can carry it."
兄は口が軽いから、秘密なんて守れっこないよ。
ani wa kuchi ga karui kara, himitsu nante mamorekkonai yo.
My brother can’t keep his mouth shut, so there’s no way he can keep a secret.
今から行っても、コンサートのチケットなんて買えっこないよ。もう全部売れちゃったって。
ima kara itte mo, konsaato no chiketto nante kaekkonai yo. mou zenbu urechatta tte.
Even if we go now, there’s no way we can buy concert tickets. I heard they’re all sold out already.
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