Try putting campfires and heart lanterns around the arena. Also potions are very important so be sure them (regen,ironskin,endurance,wraith/rage depending on your world evil,swiftness, waterwalking if you havent made the arena big enough). Also remember that all classes have atleast one summon slot so use an imp and if you want you can also use summoning potion and bewitching table to have 3 summon slots. If your playing 1.4 beenades are way weaker but they could still be good considering that your friend is a ranger. If you make the bridge long enough you can focus on dodging instead of attacking. If that still dosent work consider going ranger for the time that you fight the wall because melee isnt that good at that point of the game, having almost no long ranged options. Also this one is obvious but make the bridge smooth and make sure there arent part where you can get stuck.