In original Star Wars KOTOR HK-47 was calmer, revealing his sociopathic side mainly during specific situations. In the sequel, he transformed into a more aggressive killer robot, a desire to slaughter all meatbags consistently.

Shadow has always seemed like a cliché character to me. But yes, it was in his own game when they transformed the character into a kind of Wattpad fanfic written by Zach Snyder.

For a recent example

Phillip Graves in the Modern Warfare reboots. In Modern Warfare 2 he is a likeable, charismatic, but ultimately competent and shrewd leader. In Modern Warfare 3 he is reduced to a bumbling background player whose every line contains some form of an attempt at a joke and who becomes inexplicably a moron.

Starting off as the edgy, more cutthroat version of Sonic, only to show that he’s just a severely damaged individual who lost everything he cared about, and with the help of the other characters, is able to move past his trauma and become one of the heroes.

I think your example is the opposite :p In order to be flanderized, Shadow would have needed to be a traumatized edgy individual and then becoming edgier after that ;)

Knuckles, in the other hand, started as a strong guardian who was easily deceived… to being dumb, because he was previously deceived ^^;

The master chief

Id say its not exactly flanderization but the portrayal of Kratos past in the enw GoW games is a flanderization of his character in the old games.

People legitimately think he wasnt a complex and tragic character in the old games and they finally fixed him and made him interesting. Like did we play the same games

Sans

TIL people actually take Sonic the Hedgehog seriously

For me it’s Johnny gat, saints row originally he is someone you would want to hang out with and then by “gat out of hell” he is just someone you would want to hang