After the 1992 Olympics he teamed up with Csaba Horváth, and the pair dominated the doubles for several years. They won their first gold together at the 1993 World Championships, and after winning a record of five gold medals at the 1995 World Championships they crowned their cooperation at the 1996 Summer Olympics by winning the gold in C-2 500 m in a photo finish  and a bronze medal in C-2 1000 m. They won a total of 11 World Championships gold medals together in C-2 and C-4 events, and between 1993 and 1998 there were only two major international competitions where they did not win the C-2 500 m gold medal.
After Horváth's retirement in 1998, Kolonics started to focus on the singles and at the 2000 Summer Olympics he won the C-1 500 m gold medal. Afterwards he returned to doubles again, teaming up with the younger György Kozmann. The pair won a bronze medal at the 2004 Summer Olympics in C-2 1000 m, and a gold medal at both the 2006 World Championships and the 2007 World Championships in C-2 500 m. They were also to represent Hungary in both C-2 500 m and C-2 1000 m at the 2008 Summer Olympics. This would have been the fifth Olympic Games for Kolonics, who was also being considered to carry the Hungarian flag at the opening ceremony (this honour later went to kayaker Zoltán Kammerer).
Kolonics died on July 15, 2008 in Budapest of cardiac arrest. He lost consciousness during training and the attending paramedics could not save him. Autopsy found a small amount of plaque in his coronary arteries which might explain his death. Following his death, a press debate evolved between his long-time trainer Róbert Ludasi and the Hungarian National Ambulance Service (OMSz). Ludasi blamed the ambulance for arriving to the spot allegedly only after 37 minutes and having no defibrillator in the car, while the OMSz claimed that paramedics came in 17 minutes and started to defibrillate Kolonics almost immediately afterwards. They also said that bandages were found on the canoer's body (the existence of which was denied by the trainer) to reduce muscular fatigue, which is potentially dangerous for people having heart problems. Finally the Hungarian Canoe Federation (MKKSz) and the OMSz settled the matter with a joint statement on July 21, with Ludasi rendering thanks to the paramedics for their "conscientious and high standard" attempts to revive Kolonics, and the MKKSz declaring that the bandages were pre-tested and their procurement authorized by the Hungarian Olympic Committee.
After the death of Kolonics some (including world champion canoeist Attila Vajda) suggested that his spot should not be filled in the Hungarian Olympic team, thus Hungary should not start a unit in the C-2 events of the 2008 Olympics. Kozmann himself initially refused to take part in the Olympics, but eventually changed his mind after consulting with his coach, friends and Kolonics's friends. He competed in the C-2 1000 m with Tamás Kiss finishing in third place, while the C-2 500 m spot went to brothers Mihály and Mátyás Sáfrán.
Vajda wore a black armband in memory of Kolonics during the 2008 games.