With great power comes great responsibility, originally With great power there must also come great responsibility was a phrase Uncle Ben told to Spider-Man when Peter was going through teenage angst.
After Ben's death, the Peter took the time to reflect on himself and the mantra and eventually decided to make it his life's motto. Although the motto is applicable to all stages of life, it is especially relevant to mutants/super-humans. Keep in mind, when Peter, and many super humans first found they had super powers, they used it for personal gain.
Yet all super-heroes as we know today have gone through the process, understanding their responsibility to protect and further mankind.
List of Issues the Line Has Been Stated
Silver Surfer Vol. 3 #108 - After his powers are returned, the Surfer realizes that he cannot live a casual life as others do, "I am the bearer of great power -- and with great power, great responsibility!"
Annihilation: Nova #3 - Quasar tells Nova that he has the Quantum Bands and Nova has the Nova Force...and that he needs Richard's help. He then, thinking of their powers, says "Someone once told me that with great power must also come great responsibility." Nova thinks it sounds like something Captain America would say but Quasar tells him it was actually Spider-Man.
Evil Ernie: Youth Gone Wild #2 - Lady Death says to Evil Ernie: "With great power, comes great responsibility... to those you love"
Marvel Knights Spider-Man #15 - Ethan Edwards' father sends him on the bus with words "With great power there must also come, great responsibility"
Uncanny X-Men Annual #14 - Wolverine explains the concept to Franklin Richards and Rachel Summers, enabling them to agree to return home and try to set things right.