No baseball Records is complete wihtout the insane 1.12 ERA, the lowest ERA of the modern era... of Bob Gibson one of the most feared and unhitable pitcher in Baseball ... Not directly responsible for the fact, but his ERA and strikeouts were major reasons why the mound was lowered from 15 to 10 inches... he made sure during that year to go 92 innings with only two earned runs ... which translates in a 0.2 ERA during a 5 weeks stretch
In the same year, 1968, he also made sure of striking out 17 Hitters during the World Series... another record likely to stand a very long time ..
I am not sure anyone has gone below the 1.51 ERA Dwight "Doc" Gooden recorded in his sophomore year... (Doc could have been one of the best ever.. mind wasn't strong enough to resist the lures of drugs ... OT but Dewberry and Gooden remain in my mind the poster Children of Wasted potential for Greatness.
Every one will be broken. Might take 80 years or more but as long as they play the game some young gun will come up and do what we think can't be done.
I was basically restricting it to baseball's modern era. Otherwise you could throw Jack Chesbro's record for wins in a season. Baseball was a different game back way back when.