Lorenzi was born in Belgium and started climbing at age 2 with his father Claude Lorenzi, who was one of Belgium's leading rock climbers of the 1990s, and who created Belgium's first 8c (5.14b) graded sport climbing route, La traction universelle, in 1994.[3]
In February 2021, Lorenzi made the first ascent of Soudain Seul, a sit-start to Dave Graham's 2008 8C (V15) graded bouldering route in Fontainebleau called The Island, which was later extended by two small moves by Vincent Pochon in 2010 to become The Big Island, also at the 8C (V15) grade.[4]Soudain Seul was considered one of the "last great problems" in Fontainebleau.[5] Lorenzi proposed a grade of V17 (9A), and at the time, the only other boulder in the world with such a grade was Nalle Hukkataival's 2016 problem, Burden of Dreams. Subsequent repeats by Nico Pelorson in 2021 and Camille Coudert in 2022 softened the likely grade to V16/V17.[6]
In December 2022, he became the fourth climber to repeat Shawn Raboutou's 2022 problem Alphane, which has since become accepted as having a grade of V17 (9A).[7] After completing Alphane, Lorenzi said that he felt Soudain Seul was at least as hard as Alphane.[8][7] In December 2023, he became only the third climber to repeat Burden of Dreams, the world's first-everV17 (9A) graded bouldering route.[2]