I forgave all of you.
I forgave some bad thing that my friends did to me. Later after a month, I'm telling them the above sentence. Is this the way a native speaker will say?
While “I forgave all of you” is fairly natural, I believe native speakers are somewhat more likely to say “I've forgiven all of you” in the situation described. “I've forgiven all of you” implies that the forgiveness continues into the present.