Starting off gently, here's some major twists or spoilers from Bioware developed games of yesteryear, enjoy!
Knights of The Old Republic
YOU are Darth Revan.
Master Li is Sun Li and betrays YOU.
Just highlight the text to get the desired spoilers, be warned though, these were some of the best & most unexpected twists in gaming history at the time. Expect more hubris over the next few days, tomorrow may bring further throwbacks, until there's time to start spoiling the latest releases (by playing them first, or spoiling them for myself...).