Xasthur - Burzum - Darkthrone - Venom - Motorhead - Saxon - Iron Maiden - Fates Warning - Rush

Morpheus Descends - Sacral Rage

Morpheus Descends > Immolation > Morbid Angel > Possessed > Venom > Motorhead > Carnivore > Voivod > Watchtower > Sacral Rage

Architect of Dissonance > End of the Dream

Pretty long-ass if you ask me
Architect of Dissonance > Ingested > Katalepsy > 7 H. Target > Gigan > Deathspell Omega > Dødheimsgard > ... and Oceans > Trollheims Grott > Thyrane > Dimmu Borgir > Dismal Euphony > Theatre of Tragedy > Delain > End of the Dream
.
Kyuss -> Marty Friedman

Kyuss - Mindfunk - Faith No More - Buckethead - Marty Friedman

Nasum - Mournful Congregation

Nasum -> Nails -> Black Breath -> Dismember -> Autopsy -> Winter -> Disembowelment -> Thergothon -> Mournful Congregation

Anti -> Pro-Pain

Another day, another Fenrizposting ( and I hope you meant Anti the dsbm band and not the thrash one)... anyway
Anti > Nyktalgia > Burzum > Darkthrone > The Exploited > Suicidal Tendencies > Pro-Pain

Sound Barrier -> Darkspace

Sound Barrier - Malice - Raven - Venom - Bathory - Burzum - Paysage d'Hiver - Darkspace

Demolition Hammer - Earth

Demolition Hammer > Exhorder > Prong > Godflesh > Jesu > Nadja > Earth

Opera Diabolicus > Rings of Saturn

Opera Diabolicus -> Therion -> Amorphis -> Opeth -> Black Crown Initiate -> Fallujah -> Rings of Saturn

This one will require looking at bands with 1 recommendation...

This Belief -> ΨThatΨ

ΨThatΨ has no similar artists...?

That would make it impossible, wouldn't it? I could have sworn they had Yhdarl as a similar artist.

Scrap that then.

Hevisaurus -> Enmity

7 steps: Hevisaurus → Lordi → Death SS → Mortuary Drape → Necros Christos → Incantation → Portal → Enmity

New one: Kreuzweg Ost → Mamaleek

Kreuzweg Ost -> Ice Ages -> Summoning -> Murmuüre -> Mamaleek

Planet X -> The Austrasian Goat

Planet X > Exivious > Obscura > Augury > Ne Obliviscaris > In Mourning > Swallow the Sun > My Dying Bride > Void of Silence > Arcana Coelestia > Urna > The Austrasian Goat

Granatus > Beyond the Black

Let's take this a step up. Judas Priest > Surrender of Divinity.

Granatus -> Tank Genocide -> Zarach 'Baal' Tharagh -> Ildjarn -> Burzum -> Darkthrone -> Bathory -> Enslaved -> Emperor -> Old Man's Child -> Mystic Circle -> Siebenbürgen -> Trail of Tears -> Sirenia -> Beyond the Black




Judas Priest -> Accept -> Motörhead -> Venom -> Sarcófago -> Impiety -> Surrender of Divinity.


Neckbeard Deathcamp -> Warlock

Neckbeard Deathcamp > Marxthrone > Darkthrone > Venom > Judas Priest > Accept > Warlock
Famishgod -> Scumpulse

Famishgod > Mythic > Coffins > Celtic Frost > Darkthrone > Armagedda > Watain > Young and in the Way > Scumpulse

Infernal War > Awaiting the Autopsy

Infernal War - Belphegor - Blood Red Throne - Prostitute Disfigurement - Devourment - Gorevent - Myocardial Infarction - Awaiting the Autopsy

Hardest part of that one was sorting out all the stupid "medical term" band names.

Phobia (US grind) - Sloth (US shit/noise)

Phobia > Brutal Truth > King Parrot > Iron Reagan > D.R.I. > Corrosion of Conformity > Crowbar > Melvins > Sloth
Spastic Ink -> Jex Thoth

spastic ink - watchtower - fates warning - iron maiden - dio - sabbath - electric wizard - jex thoth

let's go for the edgy stuff:

aryan 88 (lame ass nsbm) - gevolt (jewish folk metal)

Aryan 88 > Ravensbruck > In Ketten > Absurd > Graveland > Bathory > Moonsorrow > Enslaved > Opeth > Oprhaned Land > Dibbukim > Gevolt

NRIII > Epiclore

NRIII -> Wold -> Jute Gyte -> Blut aus Nord -> Abigor -> Emperor -> Enslaved -> Bathory -> Venom-> Motörhead -> Tank -> Iron Maiden -> Helloween -> Kamelot -> Sonata Arctica -> Epiclore

whew... only 15 steps.

I could probably shorten it if I went with low-numbered recommendations.

Gnargoyles -> Mentors

Six degrees.
Seeing that both revolve around punk...
Gnargoyles > Gloominous Doom > Ghoul > GWAR > S.O.D. > Carnivore > Mentors
Low threshold votes for this one.
Lutemkrat > E.N.D.

There are no similar artists for neither of those bands

They have one and two votes, hit the vote for similar artists buttons to see. I mentioned they are below the three vote threshold

Oh yes, I did not check that

Lutemkrat > Nargaroth > Coldbound > Wolfheart > Amon Amarth > Dark Tranquillity > Soilwork > Disarmonia Mundi > Sybreed > Meshuggah > END

X-Mas Project > No Zodiac

X-Mas Project > Trans-Siberian Orchestra > Ayreon > Dream Theater > Watchtower > Death > Gorguts > Malignancy > Parasitic Ejaculation > No Zodiac
Dragonland -> Nails

Dragonland > Numenor > Stormlord > Ex Deo > Behemoth > God Dethroned > Carcass > Napalm Death > Nails

Voltumna > Pin-up Went Down

A neat six.
Voltumna > Ade > Septicflesh > Scuorn > Inchiuvatu > Akphaezya > Pin-up Went Down
Hellsaw -> Fredrik Thordendal's Special Defects

Hellsaw > Sanguis > Dissection > Shylmagoghnar > Insomnium > In Flames > Gojira > Fredrik Thordendal's Special Defects

Visionatica > Six feet under

Visionatica > Within Temptation > Theatre of Tragedy > Tiamat > Triptykon > Cianide > Accidental Suicide > Six Feet Under
Mesarthim -> Sparzanza

Mesarthim > Neurotech > Sybreed > Meshuggah > Gojira > Mastodon > High on Fire > Sleep > Kyuss > Mustasch > Sparzanza

Whoretopsy > Anti-Mortem

Whoretopsy > Ingested > Waking the Cadaver > Pencil Lead Syringe > The Red Chord > All Shall Perish > Divine Heresy > Lamb of God > Pantera > Anti-Mortem
Alunah -> Aonikenk

Alunah > Bloody Hammers > Ghost > Satan > Iron Maiden > Baron Rojo > Riff > V8 > Hermetica > Almafuerte > Aonikenk

[In Mute] > Gostwind

[In Mute] > The Agonist > White Empress > Trail of Tears > Dismal Euphony > Dimmu Borgir > 閃靈 > 陰陽座 > Gostwind
Henker -> Vanize

Henker - Origin - Decapitated - Vader - Slayer - Overkill - Accept - Vanize

Cult of Luna - Manowar

Cult of Luna > Ghost Brigade > Amorphis > Therion > Nightwish > Celesty > Axenstar > Hammerfall > Manowar

The Zenith Passage > Skid Row

7 steps. Could count as 6.66 degrees... oh well.
The Zenith Passage > Fractal Universe > Augury > Martyr > Watchtower > Savatage > Krokus > Skid Row
Blind Dog -> Draco Hypnalis

Good to see the game keeps going.
I don't know these bands but I'll try:
Blind Dog -> Pantera -> Sepultura -> Slayer -> Death -> Nocturnus -> Draco Hypnalis

This might be hard but I think it's definitely possible:
Arcana -> Buckethead
Update: It's actually not that hard.