In a way - Glory.
This is one of those things where I feel thinky-fans are just looking way too far into the text and adjusting it to the notions they want it to fit to. Glory was, technically speaking, too big of a bite for the -verse to take on. A God. How could Buffy possibly beat a god? Well, she can if we make the god intensely dimwitted and kind of docile and definitely shallow even in her non-repressed states.
For example, people who were born extremely wealthy oftentimes have characteristics that are the result of never having their power (so to speak) challenged and as a result never having been challenged to be different, to change, to grow, etc. because there exists no external pressure or stress to motivate that change. Glory can easily be interpreted along the same lines: she was an undisputed God of her own hell domain, and never experienced a serious challenge to her power. Especially over the course of millennia, she could indulge or fall victim to her own personal vices (or if she had them from the beginning, she never needed to outgrow them), her vanity and shallowness and laziness and more, because there was no outside pressure or stress to force her to change or adapt or evolve. A look at the history of powerful people in Western history, popes, statesmen and more, will furnish many examples of people with gross character flaws far more numerous then the average person, because they can afford to be. I don't think it requires a too-thinky person to think the presentation of Glory made sense.
And also, Glory is evil, from tip to toe. She always has been. I imagine evil people (with lots of undisputed power especially) like being vain and worshiped and self-indulgent. I imagine they are more likely to be that way, because I imagine evil people can see no problem with it and they probably feel entitled to all of that too. A God as evil from Glory from the start, God of her own hell domain for as long as she was...I was surprised she didn't have more fatal character flaws then she did to be honest. I imagine a truly
evil God with unchallenged power would be vain, shallow, conceited, arrogant, etc. and
like it, and
enjoy it...and indulge in it, of course.
I like that Glory is what she is in the show. I thought it was interesting to watch an evil Hell God of her nature especially have to come to terms with her lack of humanity (all her numerous flaws of course add up to total lack of humanity) when removed from her hell dimension and forced to have to account for the first time with other things, like humanity, a conscience (eventually, if only briefly and misunderstood) other powerful people with power that could challenge her, even if only briefly, people with the
audacity to challenge her, etc. It didn't change her, but that was part of the interesting thing about S5. I was intrigued by Glory's psychology.
But, although she's powerful, the writers have to make Glory really stupid, careless and lazy for the middle half of the season to suspend disbelief.
Although the 'defeating her out of nowhere' isn't S5's problem- the ways they beat Glory are cleverly scattered throughout the season and then come to a head at the end.
I think her stupidity is more a function (or consequence) of her gross character flaws, which I think are easily enough explained by what I explained at the beginning of this post^^^. Or in other words, she's not stupid really, so much as just SO vain and shallow etc. that she makes difficult decisions to understand by normal people, and that seem stupid without knowing her background. I think there is a difference: not stupid, that wouldn't be quite accurate considering where she came from, it's just the logic of someone extremely shallow, vain etc. which admittedly can sound very foolish or stupid sometimes to the rest of us. Her logic can make sense or be internally consistent though, within the context of what she is, whereas stupid people often are incapable of that.
