My serious answer after some thought.. Walmsley. Grind in obscurity for years before dropping some insane achievements at the pinnacle of your sport, become somewhat of a household name (Jim's exploits including his Olympic trials run were hyped in such rags as the NYT) , and secure a cute gf/wife along the way. A legend in his own time.
Alex Honnold free solo'ed El Capitan, risking his life for his love of the sport and moving forward what we believe humans are capable of.
That's probably as close as any climbing wuss is going to get to Matt Fox walking in a 2:26 marathon while enduring a bit of cramp in his thighs and vlogging about it for the next 6 months. Although Alex did it once then never again, Matt will be doing this over and over for years to come. That's bravery.
Not exactly what you're looking for but Ueli Steck did amazing things to meld the running/endurance approach and the climbing world. You don't have to worry so much about the weather on a 8000m peak if you can get up and down in less than a day.
For real though. Honnold and Kipchoge are basically the only two athletes from their sports to reach the relative mainstream and both are (supposedly) separated from their competitors due to their mental edge.