10 Invincible Moments That Shocked The World

As a well-meaning superhero from pretty much the offset of the comic, Robot - also known as Rudy, or later Rex - seemed like he was set to be a completely loveable good guy for the comic's whole run.

Then, after at least a hundred issues, Robot goes fully off the deep end, having come back from an alien world where he was dictator, which left him convinced he would be able to do a better job with Earth than those currently in charge. As such, Robot murders a bunch of heroes he thinks might stand in his way, traps Invincible in an alternate dimension, and then kills Cecil, the former head of the Global Defense Agency, and then takes his role.

It's an absolutely brutal turn for the hero, as he suddenly becomes substantially more morally complex, as well as substantially less trustworthy. But then, he does end up being a brain in a jar at the end of the series, so maybe it all balances out.