The most difficult things to learn to draw

[NickRowler]

Cars. My stuff always ends up looking too cartoony or like a toy.

Buildings (exterior). It's perspective mixed with repetitive images which I tend to not really have the patience for. But I love it when someone can do it well.

Boobs/Feminine bodies. I feel like I am not good at drawing women.

[Crusoe]

For me I'll second hands and just... General anatomy lol.
Textures can be very difficult, but fortunately you have custom brushes for that.

Also perspective and vehicles are a struggle

To sum it up: art in general is a struggle haha

[Tanako]

Honestly, I can wing all you have mentioned but one of the greatest challenge I've seen in all art is BACKGROUND. it's even to the point where artists are using 3D rendered background and honestly, if I can get a hold of that, I can wing the rest HAHA!

[ButterflyEmpress]

1: Hands: With hands, my problem is drawing them at weird angles. I'm looking at the reference and my brain goes "error error does not compute".
2: Hair: Curly and afro are the hardest. Light doesn't hit the same as straight hair and you can't just slap a halo on it
3: Clothes: It's hard to figure out how light hits clothes, especially if it's not a shiny material. Most of the time I don't add lighting at all
4: Water: Just make slightly opaque blue raspberry drink
7: Trees/Grass/Any vegetation: I'd hate to spend several hours sculpting every single blade of grass when they're not even the main characters. I know there's some kinda cheat for these, but I'm still figuring it out
8: Glass/Metal: My brain goes into standby mode when attempting to learn these
9: Feet: I find feet harder than hands because of their diagonal slant
10: Cars(Vehicles in general): Don't even get me started on bikes

Others
11: Texture: Similar to vegetation it's hard to portray if an object is anything, but smooth. You can't just slap dots, lines, etc anywhere.
12: Buildings: Architecture is just plain confusing. Also apparently some building designs are copyrighted

[iHateFridays]

Hmm besides general anatomy, I've always had trouble drawing vehicles and buildings lol

[sushy00]

Faces. Because everyone is used at looking at them, so if you make a mistake, it is very visible.

[Lady_T_Musings]

Cars was the first thing that came to mind after reading your list, but all of these are really good for taking an extra amount of thought on when drawing them out. Also Glass/Metal. That's a good one that I honestly don't see talked about as much. Ugh reflections XD.

[CursedBeasts]

1) backgrounds, especially man-made ones. Straight lines are not my friend and i always feel like my cityscapes look empty, at least in Bestia's Wrath.
2) legs and feet and butts???????
3) long muzzles on animals (i draw some werewolves and i struggle with them looking not wonky at times)
4)I straight up can't draw small petite people lmaoo
5) definitely agree with OP on boobs?????? they're not a focus of my work but i often just kinda give up on them as they're mostly just hidden by whatever clothes or armor my characters are wearing
6) def agree on clothes. I'm not a particularly realistic artist but I want my stuff to make some sense.