Massively flawed personality (not a crime in itself, aren't we all?) that massively hinders his ability to be a good manager - that would be my impression based upon the bulk of evidence of his managerial career, especially here.
Always been full of excuses and an expert at deflecting blame onto someone else, not just here but elsewhere also.
Worst of all though, I find him, in his professional capacity as a football manager, to be snide. And that is something I find very hard to forgive in a City manager. That's not to say that he is like that as a person in his private life but that is a different matter. He might be a great bloke to know and a really decent fella. I'm not really bothered about that though. My concern is his managerial ability and I don't like someone who is snide to refs, lsnide to others associated with the club, less than honest in his appraisals and whose first and foremost priority is always to spin everything he addresses towards attempting to direct undeserved praise his way. Worst of all, someone who is snide towards his own players, their ability, honesty and professionalism is something I cannot forgive.
Again, that is not to forgive players who may have acted in the same way but there is a pattern with Hughes and even if there isn't I expect a lot higher standards and a much more considered and balanced approach regarding personnel dealings from a manager than from a player.
Apart from all that, don't rate what he achieved on the pitch here at all. Bought good players with an extraordinary amount of money. That is nothing to lavish significant praise upon. More tellingly, constantly produced under par results throughout the whole of his time here.
Always had an excuse - and that excuse, whether explicitly or, more often implicitly, layed the blame for it at the feet of someone else.
I have to say, from being completely neutral regarding him when appointed, I grew to resent his managerial (and I repeat, his managerial, not his private - that would be ridiculous) personality and the traits associated with it. Not based on a lack of ability, which there was imo, but on the way he conducted himself in relation to the above. And I've rarely felt like that about a manager - more often than not I have sympathy for buffoons who happen to be out of their depth.
I appreciate that many people thought he behaved in a very dignified manner here. So maybe I have it all wrong.
And there are many other managers who are flawed and exhibit some of the traits I consider very low and have mentioned above. I don't really care about them though, they are nothing to do with City. And I don't really accept the argument of "Fergie is a senile, disgusting, cheating, vile managerial personality so everyone else must be ok in comparison" excuse/argument.