Ludvig Borga belongs in that latter category, and he is a fascinating case in that he continually got pushed up the ladder and basically beat everyone in his path. He even ended Tatanka's undefeated streak, which was especially tough for me as a devoted Tatanka fan in my youth. He seemed to be well on his way to being a main eventer as he geared up for a feud with Lex Luger. Luger ended up pinning him at the end of a Survivor Series match, but outside of that, I can't think of any time where someone actually pinned or submitted him.
And then he basically just disappeared. A nearly unbeatable monster who was actually pretty solid on the microphone for a foreigner. Instead of just grunting, he was at least able to convey anger and how easily he could crush Americans. To boil him down, he was basically a better on the mic, but not quite as good in the ring version of Rusev. And really, worse in-ring skills are the norm for this era of wrestling, as the technical skills of guys is leaps and bounds better today than it was 20 years ago. Despite all of this, after he left WWE in early 1995, he never again worked for another major wrestling promotion.
Despite having brief careers in mixed martial arts, boxing, and even in Finnish Parliament, he struggled with both alcohol and mental illness and committed suicide in 2010 at the age of 47. The saddest thing about this is that it doesn't count as any sort of surprise to me. Growing up following pro wrestling, early deaths are the norm, and it's more shocking that some former wrestlers have made it as long as they have.
Borga's abrupt ending in pro wrestling mirrored his own and many other pro wrestlers' lives, so we can still appreciate their talent while the thought of "What if..." hangs in the back of our minds.