Born in Działoszyn, Poland. At the age of 12, together with his parents, he moved from Działoszyn to Częstochowa, where he later attended high school. While living in Częstochowa, he was addicted to heroin for several years. In 2008, Mackiewicz was awarded a "feat of the year" award along with Mark Klonowski for an extensive traverse of Mount Logan. In 2009 he summitted Khan Tengri as a solo climber. He tried several times to summit Nanga Parbat in winter. While climbing with Klonowski in 2015, he reached a height of and in 2016, along with the French climber Élisabeth Revol, he reached an altitude of on Nanga Parbat. He was the first climber in the world who climbed an eight-thousander in the alpine style in winter, for which he was nominated for the Piolet d'Or award.
Disappearance
On January 25, 2018, while attempting his seventh try at a winter ascent of Nanga Parbat, known as the "Killer Mountain", in Pakistan, at, Mackiewicz had reached the summit from the Diamer side along with French climber Élisabeth Revol. At the summit, Revol noticed Mackiewicz's bad condition and started taking him down. According to Revol, he could not walk, see or even communicate and was bleeding profusely from his mouth and nose. She secured him from the wind in a crevasse, called for help and started her trip down the mountain. Mackiewicz had developed severe frostbite and snow blindness. It is also believed that he was in the later stages of high-altitude pulmonary edema and high-altitude cerebral edema. Revol had mild frostbite on five toes. Another Polish team that was attempting a nearby summit of K2 was called for rescue. On January 27, 2018, the rescue team, including Denis Urubko and Adam Bielecki, were dropped off by a helicopter at on the mountain. The team rescued Revol at and brought her to safety. Mackiewicz, who was believed to be in his tent at around, could not be rescued due to bad weather and a snowstorm. Ludovic Giambiasi, Revol's partner, wrote on a Facebook post: Revol was later carried to Islamabad for treatment. Mackiewicz most likely died within 24 hours, but the cause is unknown and his body has not been found. In March 2018, his father, Witold, received a death certificate from Pakistan, in which the date of his death was given as January 30, 2018.
Personal life
Mackiewicz was married to Joanna, with whom he divorced; he had two sons with her and a daughter Tonia. Xawery's ashes were carried to Khan Tengri. He was in an informal relationship with Anna Solska, with whom he had a daughter, Zoya; they also raised Antek, Anna's son.
