Iga Swiatek thrashed Jessica Pegula to win the WTA Finals on Monday, sealing her return to world number one. Second seed Swiatek dominated Pegula from start to finish to clinch a 6-1, 6-0 victory in a 59-minute masterclass. The 17th win of Swiatek’s career ensures that the four-time major singles champion from Warsaw will finish the season as world …