I say it because I know how alone I felt.

我说它，因为我知道，我感到孤独。

youdao

I've learned from victims' families just how alone many of them feel.

从受害者的家庭我了解到他们的孤独感，他们对杀害自己亲人的凶手的愤恨以及失去亲人的巨大痛苦。

youdao

To phone it in or run out the clock, regardless of how alone and impotent you might feel in your work, is to commit an especially tragic — for being so preventable — brand of public sin.

无论你感到工作多寂寞多没有前途，一旦你这样做，就是让你的可怜品牌背负了公共的罪责。

youdao

She also shows how the chemical Luminol can reveal hidden blood stains that the eye alone cannot see.

VOA: special.2010.05.05

To figure out even what this thing is, let alone how to use it properly. So, you know, I'm sympathetic.

就连认出这是什么东西（都很困难），更别说正确应用它了，所以我很同情这点。

经常犯的失误 - SpeakingMax英语口语达人

I barely know how to use a cell phone let alone a computer, you know,

我勉强会用手机，更不要说电脑了，你知道，

现在的孩子好可怕 - SpeakingMax英语口语达人

'Can you imagine how alone those few survivors must have felt, washing up here and seeing these hills that seem to go on forever?

BBC: The perfect trip: South Africa

But the devices are so new it is not at all clear how they compare with one another, let alone how they stack up against drugs or surgery.

FORBES: Health

The latest psychological research indicates that the amount of thought you put into a gift has very little impact on how much the recipient likes the gift, let alone how much they bond with you.

FORBES: Do Yourself A Favor And "Voucherize" The Christmas Thing