It is an interesting question to ask whether or not Ender is a hero or not. I mean he did annihilate an entire intelligent species from the universe (except one). Additionally, Ender discovers that the Buggers "never deliberately attacked a civilian population." They are not antagonistic to humans; however, Ender, and the humans, still proceed to wipe them out. Not exactly what the reader might consider a hero.
Of course Ender is for sure a hero to those soldiers that he commands. Ender works his way through Battle School to become a great strategist. He knows how to win, and soldiers eventually love and respect him for it. Ender and his army fight and win the final "simulation" and learn that it was not a simulation at all. His soldiers and commanding officers are elated and relieved that Ender was able to beat the Buggers. He is a hero to those that are in space with him. Additionally, Ender is a hero to all of the people on Earth. They see the space soldiers that are being trained at Battle School and Command School as their last and only hope of defeating the Buggers and avoiding complete extinction. When it is announced that Ender has beaten the enemy, the people of Earth are thrilled. Ender is the hero and savior of the human species.
Ender was a hero to the people because he was able to not only destroy the "Buggers" but he also destroyed their home planet. Ender had saved the world and the people loved him and worshiped him as a hero, but they also were afraid of him and he was unable to return to earth. After the final battle Card writes:
"Men in uniform were hugging eachother, laughing shouting; others were weeping; some knelt or lay prostrate, and Ender knew they were caught up in prayer."
"Colonel Graff detached himself from the others and came to Ender. Tears streamed down his face, buth he was smiling. He bet over, reached out his arms, and to Ender's surprise he embraced him held him tightly, and whispered, "Thank you, Thank you Ender. Thank God for you Ender." (pg 255)