Since you didn't specify, I can throw a curveball! Goku.
Yep that's right, Goku from Dragonball Z! He's technically a super hero in the sense that he's saved the world from destruction on multiple occasions, giving his life in some, as well as saving the whole universe.
He's extremely gentle and kind hearted, pure of heart. He even shows mercy to his enemies which is his downfall at times but it shows how soft he truly is. Not only is he pure but he's strong. He's the strongest of his universe and considered one of THE strongest characters in history as by the end of the series, his powerlevel (how power is measured in the DB world) is a 260 digit number. Just to put that into perspective, it only requires a powerlevel of I believe 120 to destroy the moon.
In my heart he will always be the best, both due to opinion and somewhat fact. I believe there are SOME DC universe characters that surpass him, but if you look around in the internet enough there are actual number crunchers who found that Goku can even best Superman who is widely considered the most powerful DC Superhero.