If Robb had walk out at the wedding and he survived what do te think he would do then? (Let's ignore the fact that he would never just leave without Talisa o Catelyn)

Well It's a good question! I partly agree with Rachel! It's not Robb's nature to give up he fights for justice to the end! But I also have to say that I don't see what he could do if he was the only one who escaped! All his men are dead, his wife is dead and his mother is dead and he saw it all happen! And he have nowhere to turn! No one lives in Riverrun anymore and Winterfell is a ruin!

So it's hard to say exactly what he would do! There wouldn't be much to do but maybe he would try to find new allies and gather fresh armies! :)

He'd never just give up. He isn't built like that. He's too much like Ned. He'd try to bring justice and defeat the Lannisters, save his sisters and free the North. He wouldn't just give up. He's stronger than that.