The Thin Man, who doesn’t appear at all.
In the first movie, “the thin man” is a missing person who it turns out had been murdered before the events depicted in the movie.
The thin man is barely present in the first The Thin Man film, and completely absent in the sequels.
And the Pink Panther was originally a diamond whose theft was investigated by bumbling Inspector Clouseau. They kept the title in future sequels that didn’t feature the diamond at all. When the series was revived with Steve Martin, I don’t know if the diamond was included at all.
I’ll wager that 20% of the box office for any given Pink Panther film came from very disappointed fans of Saturday morning cartoons.
Yes, in the first one.
Amy never shows up in Chasing Amy.
This is a suspense tactic in fiction that for some reason Spielberg gets credit for rather than Melville.
I just read some Facebook clickbait article of “Best movie set in each state”. They listed Fargo as the best movie set in North Dakota and commented on how it captured the essence of North Dakota so well 
In the movie Curucu, Beast of the Amazon , the titular Curucu only shows up at the very end.
And – no jury will convict me for spoiling this one – it turns out that there really is no Curucu. It’s all a sham
As in many books and films, the bulk of the film is about the long journey to whatever or whoever is named in the title, and a lot of these cases come close to qualifying for this thread. But I think that Dr. No and She and Ayesha-the Return of She actually have too much of the title character, once you finally get there, to really qualify.
A friend dragged me to an evening of multiple Beckett plays, ending with Waiting for Godot.
So on the way out I commented to him (loud enough for another half-dozen existentialists to hear):
Huh, wonder why they cut out the last line… “And, what of this note pinned to the tree? ‘Cold as hell out here, I’m down the hill at the pub! - - Godot’”.
Hawthorne Abendsen doesn’t show up until the final chapter of Philip K. Dick’s The Man in the High Castle (and it turns out he lives in an ordinary suburban house, not a “high castle”).
There are doctors who really are named Godot (There’s a David Godot in Long Beach, CA, for instance).
I’ve often wondered about their waiting rooms.
Surely their friends must have made the relevant jokes ages ago. Do any of them have signs reading “Waiting for Dr. Godot”, or “The Waiting Room of Dr. Godot”, something similar?
A quick search shows that there are plenty of physicians named Moreau. Did anyone ever sell them a kitchen island?
Bébé never appears in Bébé’s Kids.
Gunga Din has only a small supporting role for the title character.
The Third Man – Harry Lime – only has a few scenes in the movie.
Sheila is dead a year before the beginning of The last of Sheila
Roger Ayckroyd
Welcome Home, Roxy Carmichael If memory serves, Roxy Carmichael only appears in the movie in photos.
I Love You, Alice B. Toklas
To Wong Foo, Thanks for Everything! Julie Newmar - Newmar appears, but not Wong Foo.
It’s the Great Pumpkin, Charlie Brown…the pumpkin; not Chuck.
But is she there? After all, the title character of Weekend At Bernie’s is not absent.
She has a cameo appearance.
Come Back Little Sheba - she didn’t
Do we count Who’s Afraid of Virginia Woolf?
Searching for Bobby Fischer They never find him.
Pig The actual pig is only on screen for a minute, maybe two.
Bend it Like Beckham David Beckham is credited from archival footage, so I assume that’s on TV in the movie, but otherwise he isn’t represented.