Death Metal is the most diverse subgenre I know, with the freedom of creativity it allows it's almost hard to find bands that truly sound alike. Also emo? You sure you don't mean scenecore? I want an example of a band you think is death metal haha.
Also no rhythm? Death Metal is all about the rhythm dude, for example Decapitated's Spheres of Madness' intro riff, THAT is a rhythm exercise for the big boys.
I love death metal . But it isn't the most diverse. I would say punk is the most diverse. I have played dozens of shows and easily over half of them were made up of 4 punk bands that were completely different. Here's an example of the different sounds :
Crossover Thrash. (D.R.I.)
British Punk (The Clash)
Oi. (Sham 69)
Psychobilly. (The Meteors)
Street Punk. (Total Chaos)
Hardcore Punk (Minor Threat)
Punkabilly. (Devils Brigade)
Horrorbilly. (The Matadors)
Casual. (Old Firm Casuals)
Noisecore. (A.C.)
NYHC. (Terror)
Cyber Punk. (Left Spine Down)
Cowpunk. (The Mekons)
Goth. (Bauhaus)
Proto Punk. (New York Dolls)
Post Punk. (minutemen)
Crust. (Disrupt)
D-BEAT. (Discharge)
Grindcore. (Poser Disposer)
Riot grrrl. (The Distillers)
Melodic Hardcore. (The Descendents)
Pop Punk. (Face To Face)
Radio Punk. (Blink 182)
Skate Punk. (NOFX)
Anarcho Punk. (Crass)
Mod Punk. (The Jam)
Power Violence. (Charles Bronson)
Celtic Punk. (Dropkick Murphys)
Emo. (Fugazi)
Folk Punk. (old Against Me!)
1st Wave Ska. (Westbound Train)
2nd Wave Ska Punk. (Operation Ivy)
3rd Wave Ska Punk. (Mighty Mighty Bosstones)
Surf Punk. (Agent Orange)
Horrorpunk. (Misfits)
Riot Ska. (Leftover Crack)
Straight Edge. (Youth of Today)
Grime. (The Flatliners)
Garage Punk. (New Bomb Turks)
Gypsy Punk. (Gorgol Bordello)
I know I'm missing some though and its bugging me