Generally speaking, "my way or the highway" in most corporate environments is not particularly welcome. That said, I think it really depends on the company, the structure of your team, and what the UX designer's role truly is. In some shops, the graphic design is the UX designer (and sometimes they're even qualified to be!), so that balance is pretty easy. If your UX designer and your graphic designer are different people, you may run into a little more trouble - but again, it depends on what you're considering "the design". In my mind, from a UX perspective, I can dictate nearly all of the UX of the product and then turn it over to the designers to make it "pretty". In that scenario, I have done 100% of the (UX) design, and they will then do the graphical design. Sometimes that works, sometimes it doesn't, depending on the designer I'm working with. But if they take liberties that affect the UX, I explain why their modification looks nice but might create some confusion in the UX, and I generally get my way. The attitude of the management in your shop will have a lot to do with how much weight UX versus how pretty something is gets. Some places won't care as much about UX, as long as it looks shiny, so you're going to have a much tougher time being a benevolent dictator in those types of places.
In general, if you're banging your head against a graphic designer's work too often, educating them is a better way than flexing your authority. If a designer is working on an interactive product, they are (hopefully) on the same page with respect to delivering a quality product that people love to use. Most of the friction I run into with graphic designers comes from ignorance, not obstinance.