Eramis the Shipstealer from Destiny 2's Beyond Light expansion. She was built up in the background lore of the game and then, when she made her first physical appearance, she felt more like a generic edgelord villain trying to be cool and edgy. She had none of the personality that merited her getting enough of a following to create a new Eliksni House in the game's story.
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Techhunter_Talon
Jackiethederg
charlie from don’t starve
Champion Greninjoid
Lusamine from the Alolan Pokemon games. She was revealed to be the main villain, and then immediately defeated. It feels like they did that plot twist for no real reason, since in Ultra Sun/Moon they changed the plot to make her less important to the story and the Pokémon Company completely ignored her entire plot line in the anime.
Buffling
Ness when he came to smash
JabbaD
Dr Doofenshmirtz