For me as a new user, the worst thing about Unbounce is that I cannot use re-scaling and when working in the browser, to see the website in smaller size I have to actually change the scale in the browser, which creates many problems and is generally extremely not user friendly.
In addition, some actions I cannot undo (for some reason). Some shortcuts that are available in prototyping and design tools don’t work in Unbounce, which for me as a designer is disappointing and not practical.
Finally, we started collaborating on design with some teammates, working on the same variant since we did not think this would not be possible to save several changes simultaneously. The fact that Unbounce did not warn us about it in advance led us to lose some of the important work results.