Yes but you have to wait some time before you can fight him again.
No
In the fourth DLC at the end.
If you mean can you fight your friends, yes you can, you need to enter an Arena, there are several to find, once in the Arena you can 'duel' with your friends.
Assuming you have the 4th Borderlands DLC, the Interplanetary Ninja Claptrap is the final boss.
Borderlands traditions tend to be mixed. Please specify WHICH borderlands you are referring to.
Nathanael Greene (we fight, get beat, rise, and fight again is one of his famous quotes)
the creator of borderlands is Gearbox
Borderlands 2 is out now.
borderlands
Yes, you can fight Red again. After win against Red, you have to beat the Elite 4 Again and Red will reappear.
Bonuses where again please be specific. I think is there bonuses in the Moxis Underdome if your not talking about that then idk what you asking.
Borderlands 2 was released on September 18th, 2012.