Williams sealed her fifth WTA Finals title with a thumping 6-3, 6-0 win over Simona Halep of Romania in Singapore Open on Monday. It was also a sweet revenge for the defending champion Serena who had lost 0-6,2-6 to Halep five days ago in the group play.With the win Williams also reaffirmed her supremacy and proved why she remains on top of women's tennis at the age of 33.She also became the first player to win the season finale three times in a row since Monica Seles in 1992.