Formal:
* "Rwy'n teimlo'n ddrwg i chi." (I feel sorry for you.)
* "Mae'n siom i glywed hynny." (It's a shame to hear that.)
Informal:
* "O, dyna'n anodd!" (Oh, that's tough!)
* "Mae'n ddrwg iawn hynny." (That's really bad.)
* "Rwy'n gobeithio y byddwch chi'n teimlo'n well yn fuan." (I hope you feel better soon.)
To offer help:
* "A oes unrhyw beth y gallaf ei wneud i'ch helpu?" (Is there anything I can do to help?)
* "Rwy'n barod i roi cymorth i chi." (I'm ready to offer you support.)
You can also use a simple "Aie!" (Oh dear!) or "Dwi'n deall." (I understand.) to show empathy.
Remember, the best response will depend on your relationship with the person and the context of the conversation.