Not hard rock:
The Who. Songs like ‘Eminence Front’, ‘Sea and Sand’ and ‘Behind Blue Eyes’ are far from hard rock, and The Who had a LOT of songs like that. Love them, but not hard rock. They had hard rock songs, but it didn’t define them. Plus, they rode scooters and wore their hair neat. That will not do. Still one of my favorite bands, though.
Cream, Blind Faith, etc. All more blues based than hard rock.
Def Leppard, Whitesnake, Kiss, etc. Hair bands, glam rock, arena rock maybe, but not hard rock.
Hard Rock:
Guns N’ Roses. To me, the epitome of hard rock, ahead of AC/DC
AC/DC
70’s Aerosmith, before the video era.
Deep Purple
Alice in Chains
Pantera
Rammstein
On the Bubble:
Led Zeppelin - The could rock hard, but also did a lot of blues stuff. Docked an extra point for Lord of the Rings fanboyism. Don’t get me wrong, I love LOR, but it can hurt your rock cred.
Black Sabbath: More metal/experimental than hard rock.
Judas Priest/Iron Maiden, Motorhead, etc: Maybe hard rock, maybe metal.
Heart - They can rock as hard as Led Zeppelin. In fact, their early career was as a Led Zeppelin cover band. Go check out some of their Led Zep covers - they’re great. Docked points for their 80’s MTV soft-rock stuff and 70’s soft rock like ‘Dog and Butterfly’. Points added back because Nancy Wilson.
Van Halen - Again, capable of supreme hard rock, but too many pop songs and Gimmicky schtick.
Not hard rock, but could be when they wanted:
The Beatles: Not thought of as a ‘hard rock’ band, but they had hard rock songs, heavy metal songs, etc. And their hard rockers rocked pretty hard (Helter Skelter, Revolution, Birthday, etc)
The Eagles: Geneeally soft rock/MOR/Country Rock, but they had some blistering rock songs like “Life in the Fast Lane”. But damned few of them.
Warren Zevon: He wasn’t held to any genre of music, but listen to “Boom Boom Mancini”, “Lawyers Guns and Money” or “Jungle Work”. When he wanted, he coild rock with anyone.