imo what makes a perfect character is that they capture a certain concept wholesale, and relish/thrive in that hammy expression of said concept, a sort of just and true reflection of the concept rather than a perverce and muddied attempt at such things, only reason I think this is cause of when you see such characters written "wrong", or that they don't feel as true to the original concept as other expressions of them, a good example of that is Duke Nukem actually, there's been some pretty poor and really good versions of the character throughout the franchise's life and its pretty easy to point towards 3D as being the ideal version of he, idk thats my understanding on what makes a brilliant character and what breaks them at least. ┐(´～｀)┌
That's a pretty good way to look at it. A character really has to encapsulate a certain idea or concept and do it well, either that or be fleshed out and relatable in some way. Sometimes though, it takes all the right people to make a character stand out and not flop entirely. Take Caleb from the old FPS game Blood, if he had been voiced by anyone other than Stephan Weyte he would've come out as a cringe-worthy edgelord, for lack of a better term. Thanks to Weyte's excellent voice acting though, he comes across as the gritty, badass, undead gunslinger folks know him as.
Are there any characters that you can think of that disappointed you? Ones that maybe weren't well characterized or given much thought?