Endnote & Bonus Objectives
When selecting a Calamity quest, you can see its bonus objectives. They are selected randomly from a list of possible objectives, and their difficulty varies greatly.
By selecting a Rampage with achievable solo objectives, you can still get an A or even an S every time. But getting an S+ in solo will require a lot of luck or talent. By the way, completing the secondary objectives will earn you points, which will increase the levels of the stronghold. You will then unlock more defenses, which will often help you validate more bonuses and get a better score. Conversely, if you have big problems, you'll end up facing the boss with the bare minimum, which will usually result in a low score.
There are also fixed objectives that factor into the score, such as not dying, or killing the end boss, rather than letting the time run out.
Original content by Robin "Raiden Robin" Bouquet