Crowds. I dislike drawing backgrounds in general, but crowds absolutely take the cake. I'm very impatient when it comes to drawing, and even if I DID have the patience, bare in mind you must draw each person with appropriate proportions and adhering to correct perspective. Even if crowd members are not as detailed as main characters it still costs a lot of time and energy and would probably take me hours. That, and given that my fighting game comic takes place in a venue with a decently sized audience, is reasonably detailed, and there are many shots directed at them to see their reactions, forced me to come up with a solution:
Thankfully, Clip Studio Paint allows you to bring in 3D models of props and people, so I made a 'crowd' asset:

This crowd can be posed from any angle, and has 3 states (normal, cheering, booing). The only problem is that it is VERY slow (which is why I don't plan to upload it to the Asset Store). Still, when converted to lines (another feature of CSP) or grayscaled, it should look great for my black and white comic. Since it's new, I haven't actually used it yet!
I also have a low poly crowd (just a load of primitive shapes stacked together) which I can use for shots that are further away.

I honestly don't know how people have the patience to draw the crowds. I have infinite respect for you. If it were 40 years ago before 3D was a thing, I probably would have just gone out and taken pictures