You have the ability to retcon a character/team. What do you do? Nothing is not an answer. One More Day is too easy, so also not valid. Otherwise, go!
Retcon of Choice
Brayden Carter
Luke Davis
Black Panther is now a white South African farmer
Zachary Price
That's not what a retcon is. Go back to /pol/.
Dylan Morgan
To make the question more obvious, this is about events in continuity.
Cameron Mitchell
Barry Allen died again at the end of Final Crisis.
Andrew Harris
Actually it is. Rucka retcon Etta, and nos she is a black badass instead of a stupid chubby
James Hernandez
Ultimate Peter Parker never died
Alexander Reyes
Wanda and Pietro are actually the clones of Magneto's long lost son he didn't know he actually had, who is Xorn
Alexander Murphy
Bump
Luis Gonzalez
Peter stayed retired as Spidey and Ben Reilly stayed as Spider-Man and never died.
Hudson Reyes
Miles is now a black girl
Jaxon Gonzalez
Aunt May never got shot.
Lincoln Butler
BEST TIMELINE JUST REMOVE 616 ALREADY
Jordan Flores
Carol Danvers never woke up after Rouge absorbed her powers, she's dead and never came back
Joshua Young
Flight is removed from most heroes and villains.
Noah Johnson
Why?
Owen Phillips
Mar-Vell never got cancer.
Austin Cox
It enabled writers and artists to be lazy.
Isaiah Rivera
I'd undo the retcon they already did when they made Wanda and Peitro unrelated to Magneto again. I always liked that horrible family tree, including Vision's side of the family with Hank, Ultron, Jan, Wiccan and Speed too.
Kayden Lewis
John never gets retcon powers.
Evan Nguyen
Make Kamala’s series into a teenage girl sleeping her way with the Marvel Universe