Gohan is the son of Goku and Chi-Chi and hence, a half Saiyan-half human. Unlike all other Saiyans, Gohan doesn't grow up with the hunger of power and desire for fights. This could be a result of him having traits of his mother Chi-Chi. Nonetheless, it doesn't rule out the fact that he is also a Saiyan which allows him to have a far superior power than most fighters on the Dragon Ball Roster. After all, he is the son of Goku, the strongest Z warrior and the Saiyan with legendary status.
Gohan's fantastic and by far the most diverse character arc in the Dragon Ball franchise is full of different phases and alterations that shaped his seemingly normal life. His humanity at heart has many a time caused him to lose his control over his power boosts and go berserk into the fights. On one hand, it allows Gohan to completely demolish his enemy with his overpowered Saiyan spirit, but on the other hand, his principles, that are left aside, subconsciously trouble him for he's not a fighter who'd kill someone in a fight. All the fights he has fought throughout his journey, have been fought to either protect his loved ones or avenge their deaths.
Mentorship of Piccolo and Goku has helped form Gohan for the fighter he becomes. Gohan is a fighter with great ability and incredible strength packed inside of him, and just like his father Goku, he happened to break off the limits every time he had to face a superior, stronger adversary. But Gohan never related to his father's desire for fighting just to get stronger. Gohan always tried to put his principles and tendency of not causing damage to anyone first, and to fight for only the causes that he thinks are greater than him. This belief of Gohan is what led him to his very own shining moments in the Cell Saga featuring in Dragon Ball Z.
Gohan's best transformation came when he fought Cell in his final form. Initially, Gohan wasn't sure if he would even participate in Cell Games as he thought that Cell Games were pointless and served no good to humanity or any other cause. This held his powers back when all the other warriors were being tormented by Cell. It was Goku's ultimate sacrifice to save all the rest of mankind, by teleporting himself with Cell to King Kai's place for the explosion. That triggered Gohan from the inside and thus, he was not frightened like others to see Cell returning from death as good as new. Gohan took it as a chance to atone for his mistakes of keeping himself held by his principles and not standing up to protect his family when he needed to. This is the first time when fans witnessed SSJ2 form in the series, achieved by Gohan. Gohan manhandled Cell like it was all suppressed in him from the start and it came out at his father's death. Not only fighting Cell, but he also tortured him with his strong blows and punches as if he enjoyed it.
Although Gohan never really liked fighting for his pleasure, yet he did put fighting ahead of his own life when it came to be fighting for a greater cause. He never felt reluctant in killing his enemies to protect the world from their atrocities. Cell arc played a pivotal role in Gohan's character arc as it unleashed the real power of Gohan and showed us how he can demolish his enemies if he once decides to let go of his boundaries. This is why he felt right and even enjoyed himself in Babidi's spaceship to fight Dabura. The classic line against Super Buu "Fight you? No, I want to kill you." showed how much Gohan has grown. He now believes in the idea that there's nothing wrong in fighting for a greater cause.
Amidst all the dilemmas of fighting or not, Gohan always wanted to study and settle down and lead an ordinary life. He has to be the only Saiyan who attended college, where he finds Videl and starts enjoying her company. He eventually marries Videl to enjoy a normal life and now also has a little daughter. This shows that he never changed and at heart, he is still the same humane and pacifier he always was.
His early training days with Piccolo and encounters with villains like Frieza and Cell shaped the fighter in him but his lifelong experiences around ordinary people shaped the softhearted human he turned out to be. No doubt, there have been episodic events where he had to show his Saiyan warrior side for the ultimate good but if you ask me, his human side was always dominant in his character. Gohan has to be credited with the best and most diversified character arc in the entire Dragon Ball Franchise.
Share your thoughts with me and if you think there is anyone with a better character arc in DB universe, tell us in comments below.