Lesun won by a huge margin in the exact venue that the Modern Pentathlon will take place at the 2016 Olympic Games.
The World Championships silver medallist never looked like losing the combined event which he started first as the rest of the field battled for silver and bronze.
2010 World Champion Serguei Karyakin (RUS) won a dramatic sprint in the last 100 meters for the silver medal over speedster Riccardo de Luca (ITA).
The 24 year old Russian started the day on top by winning the fencing, a position he never relinquished, despite an 11th position in the swim and a less than perfect ride.
Lesun shot his 15 shots in a super quick 37,8 seconds which allowed him to casually jog around the last 1000 meters to soak up a very satisfying victory.
Lesun, who has not won gold since 2010 and won 3 silvers in 2011 stated: "I am very happy but very tired, with the sun of Rio de Janeiro. I had a bit of a bad ride which is a small problem for me."
When asked if he is the best Pentathlete in the world he stated: "Yes, I feel like I am the best, not problem, I am on top of the world."
Karyakin, who is in a four way battle with his Russian teammates to secure one of the two places available for the Olympics stated: "I am very happy, it was a difficult competition (18 of the top 20 men competed).
My coached helped me in the run a lot to help me overtake De Luca, he just kept on saying go, go, go. Fencing was the key to my medal, I have been fencing every day, practicing very hard and I even have 2 coaches!"
The combined event world record holder De Luca who moved from 18th position to be 2nd in the last stage of the combined until a determined Karyakin steamed past him stated: "I had very fast shooting today which helped and as always I ran fast. My run helps me gain a lot of positions.
I went very hard in the first 2 laps to get in to to contention, and then I had to pay in the last lap when I could not stay ahead of Karyakin."
Chinese Zhongrong Cao had a very impressive day to clinch 4th position, with Pavlo Tymoschenko (UKR) following up his silver medal from World Cup #1 with 5th place and Nick Woodbridge holding on for a well-earned 6th.
UIPM Secretary General Joël Bouzou stated after the successful World Cup: "It is very pleasing to see so many different nations getting top positions here in Rio. Yesterday we had Chloe Esposito from Australia get 3rd, Aya Medany from Egypt get 4th and local Brazilian Yane Marques get 6th.
This, together with Cao from China winning 4th place and medals for both eastern and western Europe we are proving how truly global we are."
The Modern Pentathlon World Cup Series now head to Hungary for World Cup #3 which begins on 12 April 2012, which you can again watch live on Pentathlon.org.