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It could be construed as Scrappy Mechanic (annoying or irritating mechanics) if you could list the reasons why the main quest is annoying or irritating compared to the side quests.
Edited by KDIf it's a mandatory part of the plot sequence, it would fall under That One Level.
As a rule of thumb, if you find yourself saying something is "not technically X", there's a good chance it's a Tropes Are Flexible sort of situation. In this case, "level" is just shorthand for "section of the game's content"- whether that means a sequence of maps in a linear sidescroller or a "chapter" of a Wide-Open Sandbox's main quest line.
Edited by Scorpion451

I would like some clarification on what trope would be best suited to a main story quest that is annoying or irritating to complete? I don’t think That One Side Quest works because it’s not optional, and I don’t really know if That One Level is appropriate because it’s not technically a level?
Any input would be appreciated.