As much as it results in an interesting villain, I can't get over the fact he is the result of bad writing and out-of character action.
I mean, Rapunzel was justified in making a priority of taking care of her kingdom and had no way nor time to help Varian, but the moment the threat was over, it simply doesn't make sense she didn't come immediately to him to see if now she can help.
Instead she is just sitting lamenting on how she wasn't able to help Varian then. WELL, YOU CAN, NOW, GO RESCUE HIS FATHER INSTEAD OF WORRYING ABOUT SOME MURAL.
Not really blaming Rapunzel, there, but rather the writers who needed to have their villain and didn't even made the effort to come with a good reason as to why she couldn't come to his help afterward.
Even worst, when Varian sent a message asking to unlock the scroll, right there, right now, they could have met and think of a solution.
Because of that, Varian becoming a villain seems to artificial and forced. They wanted a villain with a sad origin, but I can't get into it because they had to make Rapunzel (and everyone else) act so out of character for it to happen.