What is a respectful way to refer to a person who has died?

"Rest in peace" should always be written as RIP (which really is an abbreviation of the Latin). It should not be used as an adjective. Thus, one cannot say

The *rest-in-peace guy was a very generous man

except one wants to be extremely informal, but this is certainly not respectful. I propose two options:

1. Use deceased:

   • The deceased was a very generous man

2. Punctuate any reference to the dead with RIP (written), may he/she/they rest in peace, or may his/her/their [gentle] soul[s] rest in [perfect] peace:

   • The man, may his gentle soul rest in peace, was very generous.
   • He was a very generous man; may his gentle soul rest in peace.
   • Mr. M, RIP, was a very generous man.
   • Mr. M, may he rest in peace, was a very generous man.

3. Use while alive:

   • While alive, he was a very generous man.
   • He was a very generous man while he was alive.

4. The past tense and tender memories can also suffice, depending on context:

   • He was a very generous man.

As always, one's tone is most important factor in situations such as this.

You can say "late" if you are referring to the deceased's name, or a position from which it is obvious who you mean. This is respectful, formal, and businesslike.

The late John D. Rockefeller was a very generous man.

My late husband was a very generous man.

But not

*The late guy was a very generous man.

I would refer to the deceased unless I was aware of a particular sensitivity in the culture or context.

The deceased was a very generous man.

Some might suggest the dear departed but I find this archaic and a little patronising.