Originally Posted by Vindicator51
Yes, you need to kill / finish each of them with Killer Weapon or Rampage. This does not need to be done in the same fight. As long as you keep track of what you did, you just use stage select to finish them with the other.
What i did is was use stage select and i did each boss fight twice caus you start at the mission marker soon as you finish and if you do the killer weapon first you will have rampage for the second fight.