Most Shocking Turn Between Evil and Good?

What would be your most shocking 'long term' good to evil or evil to good switches ? Please list ones that would be explainable and make sense (Mephinsto is a demon and lives through evil thus he'd never be good). Captain Anerica being human could just 'snap' so he would be possible. Superman has plenty of bad versions of himself so I don't feel it would be much of a shock. Batman turning flat out evil? How about Darkseid or Thanos joining the JLA and Avengers? _____ also what were the most shocking turns for you, that have taken place?

What would be or what was?

Both...

Red Skull turning good...that would just be wrong... <_<

@War Killer: Or finding out he was right the whole time. Instant Marvel boycott.

Lex Luthor helping Superman, eewwww. Superboy Prime turning good would be cool. Add an overpowered Superman to the Justice League.

Magneto becoming an X-Man.....oh........
 
Sabretooth becoming an X-M........oh wait 
 
Juggernaut becoming an X.......oh crap
 
Sebastian Shaw becoming an X-.............oh f**k it, I give up

I always like dr. doom being the good guy. Its someing thats laughable.

Magneto becoming an X-Man.....oh........  Sabretooth becoming an X-M........oh wait   Juggernaut becoming an X.......oh crap  Sebastian Shaw becoming an X-.............oh f**k it, I give up

@cattlebattle said:

Magneto becoming an X-Man.....oh........ Sabretooth becoming an X-M........oh wait Juggernaut becoming an X.......oh crap Sebastian Shaw becoming an X-.............oh f**k it, I give up

LOL!

and Joker having a change of heart and deciding to join the JLA...and actually receiving membership.

Aunt may turning evil

Alfred killing a robin

Those would actually be interesting if done right. We find out that Alfred has been a mole for some long time Batman villain this whole time ... Lmao Batman fans would go nuts. Aunt May would be a little more difficult but it would be funny seeing Peter's reaction. Maybe she was the one that set uncle Ben to be murdered...____ Batman turning bad and Joker turning good would be crazy lol. Batman snaps and starts killing off villains Punisher style. Joker runs for help from the JLA or Teen Titans. Batman uses their weaknesses against them and kills off a few lowered powered heroes (in self defense 'in his eyes). Joker saves Superman from some kind of Kryptonite trap and is nearly killed by Batman for it but is saved by Supe. Superman finally gets a fair shot at Batman and takes him down hard( as he always should). Bruce Wayne is locked up in Arkum but of course soon escapes. Batman catches Joker and drops him from a building killing him. Nighwing swings in and Batman and Nightwing fight to the death. Nightwing wins and takes over as Night Bat or Bat Wing or whatever in his old mentors honer but never takes the suit or full name of Batman being that it is now tarnished.