You can use any weapon and any enchantment, but only defaults: no special weapons like Critbringer or Eventide. Remember, this is theoretical, so don't factor in cost or resources: there's no real limit here.
"Considering anything above 50 DPS is already OP, I don't know what to select..."
Its really not... against powerful bosses, even 1000+ dps is weak. If youre still havin a hard time, look at it from a pvp perspective: enchanted diamond gear massively reduces damage, even in vanilla, and powerful boss monsters have similar amounts of resistance.