Image: Rebel Wolves / Bandai NamcoOfficial screenshot from Rebel Wolves / Bandai Namco.
Dead Man Talkin' is earned the first time you question a corpse with the Compel Soul spell. The story hands you the moment early, so nearly every player gets it.
Cast Compel Soul on a dead person and talk to them. The trophy pops once the conversation starts.
Guides say you use Compel Soul as part of the story quest Smoke and Ashes, so it comes up naturally.