The Cowardly Lion maybe. Check out his fight with Renaldo Snipes. Totally bailed. It was laughable to hear Lou Duva screaming at the ref "Hey, he wasn't down, he was just looking for his mouthpiece." I will give you this, however, there was always excitement and drama in a Johnny DuPlooy fight.
Mister Snipes perfected the Phantom Punch. Johnny du Plooy - Heart of a Lion, Stamina of a Koala. The guy underachieved because training camp took place in bars and beds.
Bowe, pretty sure Futch has even acknowledged it People will say Tyson had wasted potential because of partying and dropping Rooney, but really his style was going to be short lived regardless and he remains the youngest heavyweight champion in history He was still pretty murderous post prison, but given his shorter reach and diminishing reflexes Holyfield's countering and Lewis' size would have been obstacles even with Rooney, it's not like they would come up with something other than peekaboo in-between rounds
You can identify if a Tyson fight was before or after he left Rooney. With Rooney he had constant motion bobbing and weaving. Once he left the movement stopped and he only used motion when a punch was actually thrown at him. So, its possible the Spinks fight was his peak. Yes, he would have had the size issue eventually someone with the size and boxing ability would give him a really hard time probably take some loses. Holyfield in contrast kept working hard getting bigger and stronger and better. By the time he met Tyson he actually may have been stronger and more powerful leaving Tyson with no advantage. Remember when he split with Rooney he was still very young there would have been a lot of time to continue to improve while still being at a prime age. Then again there are many variables. Rooney himself was reported to going wild in Las Vegas. After Cus died he may have started to lose his discipline and would lose his effectiveness. Have to think there was more retaining good technique and some improvement after the Spinks fight to be had.
Vitali Klitschko. Tremendous talent and fighting spirit, but injuries prevented him from being an ATG.
He retired too early. He only had 23 fights before Jack Johnson. I believe if he continued to fight (and win) he could possibly be on today's all-time top 10 lists. A lot of boxing publications have him in the top 15 or top 20, but not top 10. Maybe he beats Jack Johnson since he was still active.
Herbie had good handspeed and a decent punch on him - he could've achieved a lot more. Audley had good fundamentals at amateur and appeared as if he was being positioned for success - in hindsight, he didn't pass the sniff test but prior, you would've thought he would at least go on to hold a world title. For him to end up worse than a Whyte or Chisora in arguably a lesser era says a lot.
He had one loss anywhere near his prime outside of Ali and won the title back at 45. Destroyed multiple contenders and a fine prime champion. 76-5 with half of it coming as an old man after ten years eating burgers. Why is poor George hated so?