This is a fairly hard question, and inherently ha bias. What I will say is this, I believe every company from Google to the startup down the street will have some fault. However, one of the largest faults I've seen in my years working is the arrogance. I have personally found startups to be some of the most humble in that regard, they'll push you to make design choices other shops won't have you make, and if you mess…
Not universal, but I find most startups I've interviewed with extremely arrogant. The nicest workplaces for me have been the old and steady companies with boring software.
Things I see a lot in startups: Lack of real world business experience, so terrible management. "we're the best" attitude pervasive in everything. Hyper focused on the technology used over the job at hand. Unrealistic expectations in general. I'm gonna be rich because I'm awesome founders club.