His first major international senior competition was the 2007 European Championships, where he finished 15th. He also competed at the 2007 World Championships, finishing 29th. Two years later, he managed to enter the top ten, with the sixth place at the 2009 European and fifth at the 2009 World Championships. In that season, he also achieved his first podium at the World Cup event, finishing third in Bratislava and placed fifth in the final World Cup ranking. Next season he won his first individual senior medal: silver at the 2010 European Championships, when the Slovak canoeists swept all the podium positions. He also became the overall World Cup champion in C1 category. In 2011 he won his first and so far the only individual medal at the World Championships: bronze, on his home whitewater course and won his first World Cup race, placing second in the final ranking. He was also named the 2011 Canoeist of the Year by the Slovak Canoe Association. Between 2010 and 2015 he always finished in top 3 in the final rankings of the World cup, after first and second place in 2010 and 2011 respectively, he was also third in 2012, second in 2013, third again in 2014 and first in 2015. From 2013 to 2016 he always finished in top ten at major championships, with one ninth and two sixth places at the World Championships and two bronze medals (2013 and 2015) and one fifth place at the European level. In 2015, he was once again awarded the title of Slovak Canoeist of the Year. His biggest individual success is the silver medal at the 2016 Summer Olympics, where he prolonged Slovak medal streak in this discipline (first five medals in C1 were achieved by Michal Martikán). Beňuš also competed at the 2020 Summer Olympics, finishing in 6th place in the C1 event.