Just find a fast move and punish his random square moves. You can even use a super on some stuffs that you block like his ground circle dash (note, the ground version, the air version just over ground is god like).
The only thing about Raiden that needs any tweak is him being able to land a super after a throw, that just needs to go. Raiden is amazing upclose but there are characters that will dominate him even at close range, Big Daddy is a matchup that's not in Raidens favor because Big Daddies armored moves, traps and throw setups can really lay waste to a even a good Raiden. A character good at zoning or controlling space like Radec or Sackboy for long range or Fat Princess for space control can really give Raiden a hard time.
Jak's another character who can do well against Raiden not only because of his space control but because of his mobility, Raiden can't land a super or a combo into one on any character in the air so characters capable of fighting well or moving around well in the air give him a hard time.
He needs tweaked but he doesn't need to be as crippled as Sackboy got when the ways to beat him aren't that hard to do or even figure out.
People say that Raiden builds alot of AP, the AP system kicks in about 140 AP and stops the combo. I think that all characters have combos that can do 140 ap (note I think, I haven't learned the whole cast but the ones I have, they can do around that AP )
As A Raiden mainer I am getting quite tired of people saying he needs a nerf. The ONLY thing that needs nerf is infinite combo which is pretty cheap, unless you know how to get out of it. Kratos is BY FAR more cheaper. I actually tested this the other day. I barely play Kratos only level 20 with him from completing arcade mode and I just used sqaure and WON EVERY MATCH I WAS IN. That is all I used was the sqaure attacks. Raiden is no where near as bad as Kratos. I have to actually think and come up with ways to enter the fray because if I don't a good player will punish me hard.
Raiden wouldn't be a problem if half of you knew how to play instead of always bringing up fake complaints. Get better. Block more.
Again, blocking doesn't help against the grab, which works while rolling.
Fresh to death