Probably dialouge...sometimes its difficult to think of something compelling for a character to say or word it our right so something makes sense.
hmm, conversations. Just got done drawing a phone conversation that went on for 3 pages. It was tiring trying to vary the panels and faces for that. And it was tiring drawing so many hands holding phones.
Maybe I should specifically say "phone conversations" because I don't think I'll mind face-to-face ones. I generally enjoy interactions between my characters, but this just got old after the first few panels 
TECH. I don't mind fantastical steampunk-y things but if it's a car or a plane etc. I just do not like drawing it.
For me, it's starting and finishing the comic and the writing. I have so many ideas that I come up with, that it is hard to focus on one idea. This is why I only create one-shots. Then there's the writing I have always been more of an artist than a writer. But because every time I have ever work with a writer, it's was just a nightmare. So I decide to start writing myself and have an artist with me.
What helps me when creating backgrounds and stuff. I use the 3d program called Daz3d Studio. The program is free, and there are a lot of free or low price asserts. It is also great for creating 3d models of your characters.
Working in traditional page layout! The more I struggle with it, the less I like it. I'd prefer to work vertically, and adapt vertical panels to page layout later for printing... but my iPad doesn't handle working at such high resolution without lagging like heck (Clip Studio) or restricting the amount of layers I can use. (Procreate.)
I know I want to be able to print my comic, so being able to adapt anything I make for print is extremely important to me. And since I'd need to be able to stretch panels across the page, my vertical canvas would need to be at least 2000px across, at 300dpi. And my iPad just... will not.
Clip Studio will give me an adequately sized canvas, but the instant I add paint-y texture and colour jitter to a brush it nopes the hell out. Procreate is all like "Sure, here's all your nice brushes and a big canvas, but you can have like... 10 layers. Have fun with that."
So I persist in working in page format, despite the fact that it slows me down and frustrates me, then adapting panels to vertical, because tech limitations mean I can't work the opposite way around.
That's honestly surprising! But there are comics like Ava's Demon and Check Please that use the vertical layout too (well kind of Check please uses both I guess). They even print like 2-3 panels per page (I think). Maybe ask around to see what settings are working for other ipad users!
Maybe consider getting a laptop/tablet in the future. I got my Wacom off ebay. I got my Cintiq 21 UX(2009) for $260 (I bought it in 2018). You just gotta be extra careful. You just gotta make sure you have a good PC. I've had my PC since 2015 I specifically wanted one with a good processor intel i-core 7, good RAM, and hard drive. It was an investment I wanted to last for years. I wouldn't recommend getting a pc from ebay. I've only ever purchased them in a store.
How long it takes me. It's very inconsistent. I'll get one page done in 3 hours then take 8 hours for the next because I get distracted so easily. Other than that? The sketch part
The more detailed sketches and lineart, they're the ones that take the most time for me and that need to be done correctly
Yeah, I'm considering a new Cintiq + Mac setup, but that's going to cost an exorbitant amount of money to ensure it's future-proof for the next five-to-ten years. (I'm wary of second-hand tech, so I'd buy new.) I could do it, but I'd rather wait a few more years before making that kind of career investment.
I mean, if I got made a WEBTOON Original or something, I'd go out and buy it all tomorrow, but so long as my comic isn't my breadwinner, I'd rather find a workaround with my current setup.
Plus, I really love Procreate! I'd like to keep using it. I think I may have found a slight workaround using a DPI trick in Procreate which shouldn't reduce print quality too much, so I'm going to draw the next episode in vertical format see how that goes!
Coloring! I love picking out the colors and doing the first few pages of a project but then having to do just that for hundreds of pages is so monotonous. I also just hate any part if the process that involves me having to look at a screen and thats mostly just coloring.
Thankfully I’m tryna get a colorist now!
Marketing, honestly. It can be really exhausting trying to keep up with every platform's shifting algorithm, knowing peak update times for them, creating engaging and interesting posts and even just trying to find out what it is that catches people's attention. And when you aren't big enough to hire someone else to do all of that for you, welp, RIP to a chunk of your drawing time 
Least favorite is probably Inking. I hold some bitterness towards sketching because it takes so long, but it's also the most creative part and I've been improving my speed lately so my opinion of it has improved a little! Inking, on the other hand, still takes me quite a while to complete but is kind of boring to me since it's just... like... tracing over what I've already drawn basically.
My sketches are messy and I like the final inked look so it's a necessary evil but it's safe to call my least favorite step xD
For me, shading. Sketching is fun, lineart is hard but rewarding, coloring is easy, backgrounds are fun to do, but shading feels like it takes too long.
when I'm no longer creating something new, just going through the motions to finish the page, I get so damn bored. It's usually shading, but not exclusively
The entire shading process,, I have a particular shading style I started using last year, and I wasn't planning to use it for my comic to save time, but I really like how it looks on my characters so I decided to anyways. It is by far what takes up the most time when making my pages, especially if a bunch of different characters are on the same page. If it's mostly one or two, it's much easier.
Though I have a feeling that backgrounds in the future will absolutely suck there's no doubt about that haha
