Games that ruined entire franchises

[PAOerfulone]

Shadow the Hedgehog and Sonic 2006.
The former is an absolutely atrocious abomination that should burn in the deepest, darkest, hottest depths of Hell.
The latter, I don't think it's near as bad as everyone says, but it was definitely a disappointment and considered to be the last straw for many old fans.
Then we got many years of average (Rush Adventure, Unleashed), mediocre (Black Knight, Rivals, and Dark Brotherhood), and abysmal (SECRET RINGS!!!) games before we got Colors and Generations.