I read a short story in an anthology around 1998 (the book could have been older than that) which went like this - A human space exploration scientific crew is exploring an alient planet (peaceful planet, as I recall) when they run into an alien spaceship (from a different planet which also happened to be there) - the aliens were telepaths.
The alien commander and first officer discuss the earthlings after a meeting and realize that the human crew are the descendants of a species (Banthu/Klanthu/Zantha, something like that) which had tried to violently take over the galaxy some 20/30/50,000 years ago and which had been beaten back by the combined might of the rest of the galaxy. They had supposedly been eliminated but they somehow managed to survive and are back in space only a few thousand years after they were completely beaten (which is something the aliens are amazed by).
The alien commander kills the human explorers via telepathy but realizes that there is no information available to locate their home planet and speculate that they will be meeting again soon given the past history of the humans.
I vaguely think there was also a fantasy short by L Sprague de Camp in the same anthology, but can't be 100% sure. Any thoughts/ideas? Thanks!