TAKOBOTO

if not.. then noone
noone but him can do this

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こんなおいしいりょうりはははおやでなくてはつくれない。

Noone but mother could make this delicious food

そうでなくてははなしにならない。

There is no point in discussing it unless that would be the case.

どんなにおかねがあってもけんこうでなくてはにんげんはこうふくにくらせない。

No matter how rich one may be, one cannot live happily without health.

くりはすくなくとも１５ふんはゆでなくてはいけない。

Chestnuts have to be boiled for at least fifteen minutes.

きみたちがくせいはきんべんでなくてはならない。

You students are supposed to be diligent.

しょくもつはいきるうえでなくてはならない。

Food is essential to life.

やくそくにはちゅうじつでなくてはいけない。

You must be faithful to your word.

きみでなくてはこのほんはかけない。

Nobody except you can write this book.

でなくては is used in negative sentences.
(thing that must be)でなくては(what can't or won't be done without first part).

sarruby

でなくては書けない＝だけが書ける＝以外には書けない＝をおいて他には書けない can be used for #5459, and with appropriate modification for #5017,but note that they are not ready replacements for other examples.

You may want to think why.

bamboo4

what's up with no one being misspelled twice?

Claytonain

its waiting for you to edit + correct claytonian. feel free to improve the content...

dc