The Survivors of the Void Add-on for Risk of Rain 2 has 6 achievements.
As 「V??oid Fiend』, beat the game or obliterate on Monsoon.
As Railgunner, deal 1,000,000 damage in one shot.
As Railgunner, beat the game or obliterate on Monsoon.
As Railgunner, fire 30 consecutive sniper shots without missing a Weak Point.
As Railgunner, get 3 kills with a single Supercharge shot while airborne.
Escape the Planetarium or complete wave 50 in Simulacrum.