Education
He finished second at light-heavyweight at the National Championships 2005 and 2006 behind Kenneth Egan.
He finished second at light-heavyweight at the National Championships 2005 and 2006 behind Kenneth Egan.
He captained Ireland's boxers at the 2012 Summer Olympics in London. O'Neill claimed all honours around him in Ireland at underage levels, as well as playing for Kilkenny U-21 hurley team. He lost to Darren Sutherland on a close decision in 2008.
He also lost out on a chance to compete at an Olympic qualifier to Sutherland in an IABA box-off. He was named the captain of the Irish boxing team at the 2011 European Championships. He secured automatic Olympic qualification for the 2012 London games in the World Amateur Championships 2011.
At the 2012 Summer Olympics in London he again captained the Irish boxing team, but went out in the last 16 to Stefan Härtel. He bore the flag for Ireland at the 2012 Summer Olympics closing ceremony. By 2015, he had moved up to heavyweight, reaching the Irish final.