Ok, if you understand that creators of crappy movie intended it to be B movie full of toilet humor and cliches,then out of this list Epic movie isn't that terrible.
Same thing but much more classy is famously terribly rated "Ishtar", which I think is vastly misunderstood and underrated.
So, I do get your point, but it seriously irks me then people throw around absolutes like"worst ever" without meaning it.
Yes, each to their own, but don't be quick to judge. I personally felt that in more than few ways recent Thor Rangarock was actually worse movie than Valerian.
Watching the movie one should realize that Valerian is based on french comic books, which predate Star wars by a Decade!
https://en.m.wikipedia.org/wiki/Valérian_and_Laureline