Radec, I've tried and it's almost impossible to survive.. BUT, I do something that helps only die to it ONCE rather than twice or even 3 times.
Whilst using PaRappa, I find a nice platform in midair and chill there, if he starts to go for me, I leap in the air and press triangle to the side, which makes PaRappa fly diagonally in midair to the ground, then I side step around.
As for Kratos, I just dive into a corner (Like Hades for example or jump right OVER him and do this trick where I make my enemy think I'll go one direction, but then go the other way instead. It manages to work most of the time.
Keep in mind, this is PaRrapa I do this with, his side circle attack helps him dash in midair which is how I do my direction trick.
For me, air dodges work much better than the ground ones, so when against Kratos' L3 try to stay in the air, and try to stay behind him since his attacks only go in front of him, also if he does manage to kill you, don't move after spawning, you are invinsible while blinking when you first spawn as long as you dont move, so that bides you a little time. Also, try to pass off his interest on to other players by getting them between you and him, if you've already dodged him once he's more likely to go for the easier target any way.
As for Radec I don't know, it's never been used against me yet, I just see a lot of Kratos supers....