A straightforward, modern Hebrew rendition would be something like
זעמו של אלוהים יעניש את נשמתך
which, phonetically transcripted, reads:
Zaamo shel Elohim yaanish et nishmatkha
This, however, is almost soul-destroying in itself since, while it is technically correct, it has no rhyme or meter. What you need is something suitably biblical in tone and poetic in nature. I would go with something like:
תנאק נשמתך בחמת ה׳
in Simulated Hebrew:
tnaq nwmtç bkmt h’
tin’aq nishmatkha beḥamat Adonai
literal translation: Your soul will writhe in pain in the wrath of the Lord.
As it stands, your expression, and my translation, is in future tense. If it’s something you wish upon them, rather than a prediction—i.e. May God’s fury punish your soul—add the prefix /shé/ to the Hebrew:
shetin’aq nishmatkha beḥamat Adonai.
Of course, the best course would be to resolve the matter amicably.
(Originally written in reply to a question at Quora.com)