And The Point Is?

Leaded Gas did a great job of keeping engines from knocking thanks to tetraethyl lead.

 Unfortunately the fumes from the chemical are highly poisonous. R-12 is a refrigerant that revolutionized the cold storage of vaccines.

 It turned out to be the first of the chlorofluorocarbons which are well known (and now banned) for damaging the environment. 

Both are the creations of one inventor: Thomas Migley, Jr. 

 Two deadly inventions seem like more than enough for one person, but his story ends with a third. 

Stricken with Polio he invented a system to help him get in and out of bed on his own.

 A tragic accident ended his life when he was caught and strangled by the system he created.