Railgunner: Annihilator

 is a challenge in Risk of Rain 2, added in the Survivors of the Void expansion. It is completed as by dealing 1,000,000 damage in one shot.

Completing it unlocks the in Railgunner's loadout.

Tips

 * It's advised to use when attempting this challenge, due to its extremely high innate damage potential.
 * Stacking and  can make this challenge trivial.