Tetsujin 28: The Movie (2005)

Blurb:
A cyber terrorist bent on revenge attacks Tokyo with a menacing giant robot called the Black Ox. Its power is so great that the entire combined might of the Japanese police is no match for it. Amid the chaos and destruction, elementary school student Shotaro Kaneda (Shosuke Ikematsu) receives a phone call from an elderly man who reveals an astounding secret... his deceased father created Tetsujin 28, a giant robot powerful enough to stop the Black Ox!

Rushing forth to save the city, Shotaro and Tetsujin 28 are met with a tremendous defeat. Shouldering his father’s desire and his mother’s love, Shotaro bravely returns to the battlefield and faces off against the rampaging giant as the entire city holds their breath in tense anticipation!

Source: www.anisearch.com/movie/5280