Im planning on making a series.
Showing how the mane 6 could have been killed, if plot armor didnt exist for the 6 of them.
Because the main cast have put themselves in grave danger on many different occasions
Starting off with Twilight, i believe she would have been killed while trying to absorb all the magic of celestia, Luna nd Cadence, who are much more powerful then her at the time given Twilight still being fairly new to being royalty.
All the magic became too much for her body, and it broke out suddenly, exploding through her.