English into Japanese

"Shitsuren wa kiken desu" is close; literally, it's disappointed love is dangerous. such-and-such can kill you doesn't translate directly into Japanese, which lacks that idiom.

i used an online dictionary to answer your question, BTW:
Japanese-English dictionary

there are others; you might be able to get a better word than kiken = danger. i settled on kiken, rather than chimeiteki = fatal, because chimeiteki is an unfamiliar word to me.

Thank you very much ^^

Thank you very much ^^

Do itashimashite