What kind of letter or email do you think is the hardest to write?

I think it depends on people. I mean, what about they don’t have any knowledge? If someone wants to be employed for some job, if they don’t have knowledge about how to write applications, it would be hard for them.

I believe that the most challenging letters or emails to write are those that involve rejecting someone as a naturally introverted person. I find it difficult to convey my genuine feelings in such a situation.