Possibly semantic point to take issue with but Frankie was never 'unstoppable'. He was gifted his first title win, was smashed by Maynard before the comebacks, beaten by Benderson and Aldo etc.
But the intent of pointing this out is not to denigrate the man but praise him. He stands alongside Hendo as probably the toughest, most tenacious hall of fame-level fighter we've seen.
He is one of the GOATs but not because he was 'unstoppable'.