Putting it mildly

Putting it mildly
 

"Por no decir algo peor" is an option to translate "putting it mildly".
Does anyone have a better translation?
Google Translator gives "ponerlo suavemente", which seems to me a bit too literal, although it may work sometimes.
Maybe "decirlo sin exagerar", "decirlo con tacto" are options. Any other ideas? :)

I would say something like: Estás excesivamente bondadoso./ o decirlo con damasiada bondad

Yo siempre lo traduzco como "para/por decir lo menos = to say the least"

Thank you, Poli and Chileno. These options are usable. :)