Here are a couple of possibilities:
* Ρενέ (Rene): This is a fairly straightforward transliteration using common Greek letters for the sounds in the name. It's likely the most common way to see it written.
* Ρενή (Reneh): This option is similar but uses η (eta) instead of ε (epsilon) at the end, potentially offering a slightly different pronunciation depending on the emphasis placed on the final syllable.
Neither is perfectly accurate phonetically, but both convey the name's essence. Context would determine which is best.