Some horrendous fashion faux pas (correct spelling, btw) in the 70s that spring to mind:
1. The "Penguin" suit, as worn on stage once in Vegas in August '75. I liked the other versions of the Flying Suits, but this was too much.
2. The Pontiac Suit, with puff sleeves and plunging curved shirt line. Just plain awful.
3. His "turban" phase. There are pics on the galleries here of him in these ridiculous head-covering creations.
4. The track suits, '76 - '77. Yes, he was putting on weight, but there were better ways to hide it. NO ONE, not even looks good in a track suit! The footage of him backstage from the unreleased Elvis In Concert footage, and getting off the plane meeting Todd Slaughter. Ugh!
Special mention: the white, terry-towelling hat he wore during his last vacation in Hawaii, '77. Nice combo with the blue track suit ... not.