Quests are arbutrary goals accessed via the goggles in the waiting room or the laptop in the hated arcade.
Kill X things X times
These kinds of quests usually involve killing screamers an absurd number of times, or killing bosses a specific number of times, like killing co-en or Max Sharp. the hardest to fufil are ones targeting the jackals, even harder the ones targeting specific jackals.
Climb from X to X without doing X, killing all enemies
These quests are difficult, especially if you are accustomed to doing the thing you're not allowed to do.
one difficult quest like this is the "climb from ikegara to imokowa-cho without dodging, killing all enemies" it's hard due to a small room in the tile set where you come in, kill a scratch tuber, and then have two options; 1. keep going. 2. destroy the crates to fight a Screamer who almost always has a ranged weapon like the Red Hot Iron or Robber Crossbow.