For me, the concept of Heroism goes hand in hand with the concept of 'Doing the right thing'. Though both concepts are completely different when implemented in the story, I feel it's nice to see an MC who is a good person.
There's an Anti-Hero trend going around where people can't make up their minds regarding the protagonists they want. A few writers would sometimes add Anti-Hero elements to their MC to make them more believable and fail miserably due to how misguided they are on the concept of what 'Heroism' actually is.
Most of you probably have no idea what I'm talking about since it's fine to make a character more relatable by giving him a darker side, but I'm sure at least one or two of you can relate to this problem.
'What problem?' Is what most of you should be thinking by now so I'll try my best getting to the main point.
What I'm trying to say is that: When writing about a heroic protagonist, you need to be more open-minded and accept other kinds of Heroism.
Not at an emotional level but you at least need to establish in your story that your MC isn't perfect in his actions.
I don't mean by adding his mistakes and clumsiness into the story but adding elements that suggest his decisions aren't always the 'Right thing to do'.
SPOILER ALERT!!!!!!
For example: In Fate/Stay Night and Fate/Zero series, there are two 'Heroes' that stand out among the other participants. Kiritsugu Emiya is the ruthless Hero who would save more lives by sacrificing the lesser amount whilst Shirou Emiya want to save everyone despite how unrealistic it is.
Both of their ideals have strengths and flaws. Shirou's ideals are too unrealistic while Kiritsugu's ideals ultimately lead him to self-destruct due to how misguided he was about his actions.
In a story where Heroism is a thing, it isn't shameful to take tips from Marvel when it comes to character motivations.
I mean, it's not like Spider-Man's reasons for being a Hero is the same as Iron-Man's or Captain America's.
Some do it for fun, some do it for patriotism, and some do it because it's basically the right thing to do.
And that's not all, the main reason I even mentioned marvel was because everyone has their own ideologies.
The author may have his own personal ideology, but that isn't mixed with the existing heroic ideologies of the MC.
Many things will start feeling out of place once you start adding your own black and white ideologies of right and wrong into the background of the story by judging your own characters actions yourself. I mean, whether the MC is a Hero or not is dependent on the readers of the protagonist, not your own.
If you do turn your character into a Mary Sue that can't do anything wrong, make him/her a paragon at least. A person who drives others to better themselves.
This is not a rant nor can my thoughts be considered the best advice out there so take this as a grain of sand.