Edward Blake (a.k.a The Comedian) embodies the cliché telling us that when we lose a loved one, they "live on" in our memories. The recent Before Watchmen series notwithstanding, Blake's murder sets the entire comic in motion, so most of what we learn about Blake comes from flashbacks and anecdotes from his fellow crime-fighters. As such, we're left to rely on the testimony and interpretations of others to speak for his character. By the end of the original Watchmen mini-series, Blake's as fully developed as the rest of the living heroes, though whether he's a sociopathic nihilist or a disillusioned realist depends on who you listen to.
Videogames in particular can take advantage of a character's absence to enlighten us about them.
This kind of posthumous characterization happens in all sorts of media - see Twin Peaks's Laura Palmer, House of Leaves's Zampanò, and the thousands of murder victims in police procedurals, for starters. When properly executed, it acts as great example of world-building, showing that the world the characters inhabit in the fiction exists beyond the events that occur within the story. And if the ability to create a world separate from the people inhabiting it (allowing characters who aren't there physically to exist) is the most important factor in posthumous characterization, then videogames may just be the best medium for properly eulogizing the dead.
Before I continue, it's important to establish what I mean when I say "posthumous characterization." It does not simply mean fleshing out characters that have died - if a character's ghost comes back to life and becomes important to the plot, it doesn't count. It also doesn't count if a character is alive, killed, and then continues to influence the story. Rather, posthumous characterization means learning more about someone in their absence. Under that definition, Zampanò is probably the most pure example of the ones mentioned above, since he doesn't appear in person at all, while both Laura Palmer and Edward Blake are depicted in flashbacks, dreams, and videotapes at some point.
Videogames in particular can take advantage of a character's absence to enlighten us about them. We see (and listen to) hundreds of short stories in BioShock's dilapidated art deco city of Rapture, like the increasing insecurity of Andrew Ryan's estranged girlfriend and an irreverent handyman's rant about getting the pipes fixed; Portal's Ratman is absent from the narrative of both games, yet his imprint can be found throughout various test chambers; Metroid's Chozo race leaves behind volumes of lore for Samus to sift through, detailing their way of life and extinction.
The importance of these stories to their respective games' central plot varies, but these stories can often be stronger than the main one. The strengths of environmental storytelling in games have been touted before, but suffice it to say you can tell the player quite a bit without speaking directly to them. Where this benefits videogames more than other mediums specifically is in characterization, because the people we're told about indirectly don't have to adhere to the mechanical language of the game. Ratman, for example, doesn't need to solve puzzles to tell his story; similarly, most of the people in BioShock you learn about through audio logs and plasmid-induced hallucinations don't have to be Splicers or gunmen. By separating these stories from the actual game, developers can tell a wider breadth of stories, not just ones that have to contextualize themselves around a gameplay hook.
It's of course possible that loading a game with a large amount of tangential information can do it a disservice. But collecting the clues and information about the dead can work just as well as the centerpiece. Dear Esther revolves around this very idea; the game has no combat or obstacles to speak of - in reductive terms, all you do in Dear Esther is walk along various paths to a goal. And while the game doesn't have any easily identifiable puzzles, you're not likely to piece together the entire story on your first playthrough, or without outside help. In that sense, Dear Esther's puzzles aren't mechanical, they're narrative - "beating" the game means building a story from the pieces you're given. And because all the possible clues are strewn about the island, without any of them being shown or described directly, the player has to sift through information and decide what is relevant.
The lack of special attention given to any particular object in Dear Esther also means the player isn't looking through any personal lenses. Placement can still invite some rhetoric - an enormous message scrawled along a cliff in white chalk, for example, is difficult to ignore - but the only lens you use to examine this message, along with the game's characters, is your own. Contrast this with House of Leaves, where everything we learn about Zampanò is told to us through the editing and notes of Johnny Truant, who's hardly a reliable narrator.