Hatsu Hioki. I remember people actually thought he was the best FW in the world. Little off topic but I wish Marlon Sandro would have been able to get in the UFC at some point
Yeah, came here to say this. I delved into hos career a bit after learning about him while researching Oliveira's old fights.
Hatsu is at least an honorable mention at Featherweight when it comes to UFC busts. When he got signed he was 24-4-2 (with notable wins over UFC vets Mark Hominick & Jeff Curran) and on a four-fight win streak, with his last loss before that being by Split Decision. All of his pre-UFC losses were by Decision, in fact -- most of them Splits. He had never been finished in his career. He was the Featherweight Champ in the Sengoku, Shooto, and TKO promotions. Hioki was also regarded as an absolute grappling wizard and many considered him a de facto Top 5 Featherweight in the world, if not the very best who would dethrone Jose Aldo with ease if he ever made it to the UFC.
Well, he got his chance. The UFC signed him and he promptly got lackluster Decision wins over fairly mediocre opponents in George Roop (who took him to a Split) and Bart Palaszewski, who was at the end of his career. Even so, the UFC was willing to offer him an immediate title shot against Aldo due to his accomplishments and standing from outside the promotion. Many still believed he was the guy to topple Jose... but he turned down the offer. He wanted to get more fights in first and make sure he was ready for the challenge.
Turned out to be a mistake. Hioki immediately went on a three-fight skid, dropping Decisions to Ricardo Lamas, Clay Guida, and Darren Elkins before regaining some of his momentum by Decisioning Ivan Menjivar (another low-level guy on a loss streak of his own and at the end of his career). Hioki then promptly lost all of that momentum by running into a young, surging Do Bronx who outgrappled the supposed grappling phenom -- the man who had never been finished -- escaping his rear naked choke attempt and reversing the position to sink in an anaconda choke of his own, giving him his first and only submission loss. Hatsu went on to face Dan Hooker, getting knocked the fuck out in the second round -- again for the first time ever. At that point the mythical Aldo-Slayer shuffled off quietly to Pancrase. He's gone 2-3 since leaving the UFC, with all three losses in a row by knockout. I guess the Hangman cracked his chin something fierce in addition to giving him his walking papers

I do feel for the guy and how things turned out.