He was distinguished for his passion, selflessness in terms of the progress of the Greek football, but especially for his beloved AEK.

He started his football career as a young player in Turkey, playing for Enosis Tataoulon, where he stayed for four years.

The kids were playing in the arenas with canvas balls full of shavings and trying to imitate "Negro's" shots, dribbles and moves.

After the Greco-Turkish War in 1922, Negrepontis, as the team's captain, took the initiative to take Pera Club on a tour in Europe, with Greece being one of their stops and in a total of 47 games they achieved 43 wins, 2 draws and 2 defeats.

In 1932 he led AEK to the conquest of the first Greek Cup, which was also the first trophy in their history, beating Aris by 5–3, with Negrepontis scoring the last goal for his team.

He made his debut against Bulgaria in a friendly match that ended 1–1 coming of the bench at the 46th minute.

He was the coach who achieved Greece's biggest victory of 8–0 against Syria in a match which took place on 25 November 1949 at Leoforos Alexandras Stadium.

He also managed teams of the likes of Panelefsiniakos, Apollon Athens, Ethnikos Piraeus,[13] Panegialios and Panachaiki.

The former president of AEK Athens and author of the first history book about the club, Panos Makridis wrote in the Greek newspaper, "Athletic Echo" about the death of Negrepontis: "As a former president, but also as one of the founders of AEK, together with the whole world of the fans, I mourn the loss of Kostas Negrepontis.

He was one of the creators of the glory of AEK, but also a brave and honest fighter in the stadiums, whether Greek or foreign.