luckily i didnt hit anybody, but as you can imagine the car isnt going anywere.

the right rear line blew, and my question is: once the line is fixed
do i have to rebleed all the brakes? or just the one?

thanks.

If it were my car, I would bleed them all and flush the system. This is because you don't know exactly how far a bubble could have gone. Also, if you lost enough fluid to drain the master cylinder then you probably have bubbles toward the front of the system as well. Without actually seeing what you've got, it's difficult to say if you can just bleed the one wheel cylinder or not. But, I'd bleed them all just to be safe.