The missed opportunity with Butterball was just messed up. You have a guy who has the holy grail of super abilities. He's indestructible...but he is also in terrible physical shape and his indestructibility seems to be what keeps him from getting in better shape.
Also around just before that time Tony Stark came up with his Super Power Inhibiting Nanites (S.P.I.N.). So why not have given Butterball a dose of the S.P.I.N. amd turn him over to someone to train him as a normal. Strict diet as well as intensive physical fitness and hand to hand training. After you get him to the level of someon like Hawkeye or Batroc you deactivate the S.P.I.N.
All I wanted was to be unconditionally loved while never having to work on my flaws. Is that so much to ask?
So many options. There are also characters like Leech, who can suppress powers. Hang out with Leech for the exercise sessions, and Butterball can work that weight off. Or he can cheat and do it the easy way with a body-sculpter like Lionel Jeffries or Masque. (Leech has already been used in that manner for other characters, such as giving Hazmat a 'day off' from spewing radiation and poison all over the place to go hazmat-suit-less to visit family and stuff, which... went poorly.)
Or, my preference, Butterball can just remain heavy, but build up some muscle and be a bit more Kingpin-like, a big guy who *isn't* soft or weak. Heck, he's ideally suited to be a heavy-set hero who pulls it off, and doesn't have to 'get into shape.' It might be nice to have a few more overweight characters who aren't villains like the Kingpin or the Slug or Sumo or explicitly have fat-based powers like the Blob, Phat or Big Bertha.
I meant with the above methods, using Leech or SPIN tech or one of the many other power-suppressing methods available in the Marvel universe. Turn off the invulnerability, exercise like crazy and stay 'powered down' for a day or two for the muscle tissue to grow back stronger, turn the power back on.
All I wanted was to be unconditionally loved while never having to work on my flaws. Is that so much to ask?
The guy is totally impervious to harm. The Hulk could throw him as a weapon. Even with his obesity they could still figure out how to maximize his invulnerability. He could go places most heroes couldn’t go. Extreme heat, under water, poisonous gas, radiation, Etc. Like you said with proper training he could be formidable. At least intellectually even if his body stays the same.