For me, a couple that stand out are when all the characters have the same faces to the point where if they change hairstyles, you can't tell them apart.
In terms of storytelling, you can have a lot of panels in an update but it'll feel really short if there's no story progression. There's a few comics I've read, where they're been sitting in the same place for probably a month or more worth of updates, only to stand up for the next two, and then go sit down somewhere else for some more updates? A lot of panels just feel copypasted and... I don't know, I just want to feel like I'm reading a visual story, rather than a slow-roll of text with a nice backdrop.
Also, when stories disregard that there's masters who have dedicated their entire lives to something, only to push them aside for the new, younger, main character, who only started practicing said craft three days ago, and is now more op than everyone in the entire story. On the same note; when all of the main cast becomes op, protected by plot armor, but we have forced deaths of background characters who were never developed in the first place.
And lastly, where everyone's loves are requited and every single main character ends up in a relationship, at the end. It just feels too forced and inorganic.