What do you dislike so much, you refuse to take it as canon?
For me, one is King Sombra's role in Season 9's premiere of My Little Pony: Friendship Is Magic:
In Season 3's premiere, and his alternate future in Season 5's finale -- he was a no-nonsense enigma whose actions/effects spoke for him. And in the tie-in comics FIENDship Is Magic and Siege Of The Crystal Empire -- he became a complex Darth Vader-type that was just as smart and serious as his on-show self, and his presence even gave said Empire more worldbuilding than ever.
...Until S9's premiere ignored said comics; gave him a cackling, cliched new persona overnight; and devolved him to the KGBeast/Slipknot of Grogar's Suicide Squad.
The way I see it -- the latter was just a defective clone/golem, and the real Sombra's arc already ended in said comics.