Damn... This is a tough one.
I'd have to go with some Thrash Metal bands like Megadeth and Metallica.
It's not so much as I don't like them. I do. It's just that I've heard so much about them before that I already know what to expect from them.
Also a few slam Death Metal bands... Cephalotripsy is no exception. The lead singer sounds like he's having a belching fit. BUT, the riffs are crushing.
And not to mention a few Deathcore bands. It's not so much as the riffs or the sound. Sometimes the vocals make my ears ache. I admit, some Metalcore bands are pretty good. But not where I'd listen to them. I actually used to listen to Suicide Silence back in the Summer or 2010 (Along with Slipknot, but that's a different genre). I quickly got out of it after my introduction to black metal.

This kinda makes me raise an eyebrow. Why would discovering a better form of music suddenly make Suicide Silence and/or Slipknot bad? The fact that you were able to "get out of them" so quickly makes me wonder if you were just pretending to like them to begin with, which kinda makes me question the validity of your listening endeavors as a whole.

I don't know why I care so much. I really don't.

Oh, and most -core variants that take more influence from metal. Always hated that stuff, even when I was just getting into metal and loved everything I heard that was even remotely heavy that stuff never sat with me all too well. Surprisingly enough, I actually like the more hardcore-tinged stuff somewhat.

Brutal Death Metal and slam for the same reasons. The riffs are all just shitty mush, and the more "technical" variants are just technical mush. Sometimes a band's so mushy it becomes awesome, like Defeated Sanity or Wormed, and sometimes a band's so technical it becomes awesome (Viraemia) but besides the odd exception here and there this stuff's terrible, and it doesn't help that record labels like Sevared and the like pretty much release 80 new albums a day with this shit, like seriously, who the Hell buys all this stuff? Somebody is, because they're staying in business.

Here's the real shocker...USPM. Yeah. My tastes in Power Metal are kind of sporadic and oddly defined, but I don't like much of this stuff. Sure, it's more "aggressive", and it caters to metalheads that are afraid of any passive, flowery melody in their music, but it loses a lot of the hookiness. I WILL admit I have only dabbled around this scene though, only hearing a few odd albums, so perhaps that's my problem. I'm just not motivated to look into it any further.

One exception though: Fates Warning. It's like a five-star riff buffet.

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It didn't make them bad or anything. I had been listening to them for so long at that point, they just became boring. And back then I went through phases in the music I listened to. I'd just stick with one or two bands, and this usually lasted only a few days. I guess this particular phase lasted longer than my other ones. And besides. With Black Metal, there are different sub-genres of it you could listen to. Deathcore and Nu Metal are... Just that. Deathcore and Nu Metal. ...Jesus Christ, who put Slipknot as Thrash Neo? e_e" I can understand the Neo part, but that whole Thrash part is dumbfounding for me.

There's a lot of different sub-sub-genres of Deathcore too, and you could argue the same about nu-metal, for instance, perhaps there's prog-nu-metal (System Of A Down) or industrial nu-metal (Static-X). I understand what you're getting at because those genres suck, but don't generalize genres, not even shitty ones

What makes you think Black Metal won't be a passing phase for you as well?

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If you are a false, don't entry, or you'll be burned and died!

The only one I know of is Symphonic Deathcore, if that even counts.
Plus, I never knew Nu Metal had any other sub-genres. I thought it was all just one.
I admit there are SOME good bands of those genres, but those were the only ones I knew. :P
I suppose it's because there's so many bands of different sub-genres of Black Metal, and it'll probably take me forever to find ALL of them. And even if I do, I'll never get bored with the genre, because if I get bored with one sub-genre, I can jump to another one.

Maybe it's just me, but I never get bored of genres. I could listen to the same couple sub-genres all day every day and never get bored of it. Like, when I buy a new album, I always digest it slowly over a couple of weeks. Obviously my listening patterns will fluctuate as I discover more good shit, but I can still go back to my favorite sub-genres and always find something to enjoy.

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If you are a false, don't entry, or you'll be burned and died!

Me neither. but it depends on what genre it is. I usually listen to a few songs from an artist a couple of times before eventually getting bored with it.