Downplayed: Occasionally Bob does a little more heroic action than necessary, but not much.
Bob's Power Source actually requires him to perform several heroic acts a day in order to function.
Bob suffers from trauma stemming from how a young girl died when he chose to do the "logical thing" and call for help rather than dive in to save the day himself. Now, whenever he comes across someone who needs his help, his fears of history repeating itself keep him from ignoring them.
One of Bob's powers is Super Speed and lives in a Sugar Bowl where there are no real problems. He helps everyone because he has nothing better to do.
Bob is a genuinely Nice Guy who just likes to help people thus when he got Powers/Skills he decided to use them just to help everyone out.
Bob never passes up an opportunity to be a Jerkass to people.
Zig Zagged: Bob acts far too heroic for his own good... but then he refuses to rescue a kidnapped little girl. The overwhelming guilt causes Bob to rescue her later on... but it turns out that that was her sister - the original little girl is still trapped! Bob goes off to rescue her, but stops mid-step. Then he goes on anyway...
Averted: Bob never performs any more heroism than the norm.
Enforced: "We need to show how heroic Bob is! Let's have him repeatedly act heroic!"
"Why can't I stop being a hero?"
"Building on fire, cat caught in tree, opening a peanut butter jar? Bob..." "Look, I don't choose who needs help with what, all right? I'm there, I help. It comes with the cape."
Invoked: Alice dares Bob to help 50 people in one day.
Exploited: Emperor Evulz sets up several dangerous situations in order to keep Bob busy while he works on his Death Ray.
Defied: Bob actively avoids minor dangerous situations.
Discussed: "Boy, is he heroic! How is he still standing after doing all that?"
Conversed: "Yet another over-zealous hero. Aren't you getting sick of those?"
After not being able to save a little girl from a burning building, Bob commits suicide.
In a way, the trope itself is a deconstruction of being The Hero.
People start to catch onto Bob's constant need to be the hero, and as a result he is easily taken advantage of.
Reconstructed: After not being able to save a little girl from a burning building, Bob resolves to help others more.
Played For Laughs: Bob brags about how he can do 20 good deeds in one hour and proceeds to do so.
Played For Drama:
The strain of the repeated heroic acts cause Bob to have a Heroic RROD.