In My Hero Academia, many of the students at U.A. have their own personal hero whom they are striving to emulate. Izuku, for example, received One For All from All Might, the aging and weakening symbol of peace, and aims to prove himself worthy of his idol. He's far from the only character working to step into a role model's shoes.
Tenya Iida is Class 1-A's president at the prestigious U.A. school, and he looks up to his big brother, Tensei Iida, as his personal hero. But while Tenya Iida has a lofty goal in mind, he falls short of his brother's morality. His relationship with his brother proves that the two Iidas are not the same after all.
Tenya Had Tensei's Footsteps to Follow In
Just like Izuku looked up to All Might, Tenya Iida looked up to his big brother, Tensei Iida. Unlike Izuku, Tenya had the chance to spend a lot of time around his role model and grow up with him, meaning Tenya had a lot of chances to learn from him: how to be a good brother, a proper man, a noble hero and more. Tenya and Tensei were close as a result. They even had similar Quirks and similar ideas on what a hero costume should look like.
Tensei became a licensed hero known as Ingenium, with a distinct set of armor. This only elevated Tenya's lofty opinion of his brother, and he strove nonstop to emulate him. Tenya's own hero costume and hero name closely mimicked Tensei's. The brothers were on track to be great heroes together, but then tragedy struck: Tensei was ambushed by Stain the hero killer, and nearly lost his life.
Tensei's Fall and Tenya's Rise
Stain is an idealistic villain who seeks to rid the world of unworthy heroes, and his deadly battle with Tensei led to more revelations about Tenya than it did Stain himself. Tensei survived the encounter, but he was left in critical condition and bedridden at the hospital. Tenya made sure to visit him, and realized that his idol was no longer fit to serve as a hero.
All at once, Tenya's role model was knocked off the pedestal, and Tenya's reaction was very different from Tensei's. Tenya sought revenge, and with uncharacteristic recklessness and anger, Tenya headed to Hosu to seek Stain and retaliate. This quest did not turn out well: Tenya was cornered by Stain and nearly lost his life. Only the intervention of Shoto and Izuku allowed Tenya to survive at all.
By contrast, Tensei was at peace with what happened, even if he was disappointed in his early retirement. He wants what's best for Tenya and is rooting for his little brother. In many ways, this echoes All Might passing his power to Izuku and carrying on his legacy through that boy. This showed great maturity and a balanced perspective on Tensei's part and showed how much faith he had in Tenya. However, Tenya felt like his relationship with his brother was ruined, since they could no longer run side by side as heroes. Tenya used his seemingly broken relationship with Tensei as a reason to seek revenge and put himself in serious danger, which contradicted Tensei's own interests.
Clearly, Tenya had a long way to go at that point as a hero and as a brother, and even as a prematurely retired hero, Tensei set a high bar for his vengeful younger brother to reach.