Question: Who won more singles titles, Steffi Graf or Heinz Günthardt?

Context paragraphs:
1989 Lufthansa Cup – Singles: Steffi Graf was the defending champion going into the final against her rival Gabriela Sabatini.  Just the previous month, Sabatini defeated Steffi Graf 3–6, 6–3, 7–5 in the final at Amelia Island, Florida.  Now, in her native Germany, Steffi would turn the tables against Sabatini, beating her 6–3, 6–1.  Prior to this match, Sabatini had played in four finals in 1989, with her winning twice.  For Steffi, this victory was her seventh of the year, and marked the sixteenth time out of nineteen matches she had beaten Sabatini.

Graf–Sabatini rivalry: Steffi Graf and Gabriela Sabatini are retired professional tennis players who played each other on 40 occasions between 1985 and 1995.  Steffi Graf was the world No. 1, whilst Sabatini reached a career high of No. 3.  They are both Grand Slam Champions, the German winning 22 titles whilst Sabatini won her only Grand Slam title against Graf.  The pair also teamed up to reach three French Open finals and won the 1988 Wimbledon crown.

2016 French Open – Women's Singles: Serena Williams was the defending champion, but lost in the final to Garbiñe Muguruza, 5–7, 4–6.  Williams was attempting, for the third time, to equal Steffi Graf's Open Era record of 22 major singles titles.  She was also attempting to become only the second player, after Steffi Graf, to complete a quadruple Career Grand Slam.

1988 Wimbledon Championships – Women's Singles: Martina Navratilova was the record six-time defending champion, but she lost to Steffi Graf in the final, in what was a rematch of the 1987 final.  This was Graf's third step towards completing the first and so far only Calendar Year Golden Slam.  It was also the first of Graf's seven Wimbledon ladies' titles.  After Graf took a 5-3 lead in the first set, Navratilova won six straight games allowing her to win the first set and take a 2-0 lead in the second set.  Graf then came back winning 12 of the next 13 games and the match.

1980 Geneva Open – Doubles: Željko Franulović and Balázs Taróczy won the title, defeating Heinz Günthardt and Markus Günthardt 6–4, 4–6, 6–4 in the final.

Steffi Graf: Stefanie Maria "Steffi" Graf (] ; born 14 June 1969) is a German former tennis player, who was ranked world No. 1 during her career.  Graf won 22 Grand Slam singles titles.  Her 22 singles titles put her second on the list of Major wins in the female competition since the introduction of the Open Era in 1968 and is third all-time behind Margaret Court (24) and Serena Williams (23).  In 1988, she became the first and only tennis player (male or female) to achieve the Golden Slam by winning all four Grand Slam singles titles and the Olympic gold medal in the same calendar year.  Furthermore, she is the only tennis player to have won each Grand Slam event at least four times.

Heinz Günthardt: Heinz Peter Günthardt (born 8 February 1959 in Zürich) is a former tennis player from Switzerland, who won five singles titles during his professional career, including the Rotterdam WCT in 1980.

1981 Stockholm Open – Doubles: Heinz Günthardt and Paul McNamee were the defending champions, but McNamee did not participate this year.  Günthardt partnered Balázs Taróczy, losing in the first round.

2016 Australian Open – Women's Singles: Serena Williams was the defending champion, and attempting for the second time to equal Steffi Graf's career record of 22 major singles titles.  She lost in the final to Angelique Kerber, 4–6, 6–3, 4–6.  Kerber became the first woman to win a singles major title after having saved a match point in the first round, which she did against Misaki Doi.  She is also the first German of either sex to win a major since Graf at the 1999 French Open.

1989 French Open – Women's Singles: Steffi Graf was the two-time defending champion, but lost in the final to 17-year-old Arantxa Sánchez Vicario, 7–6, 3–6, 7–5, ending her winning streak of Grand Slam singles titles at five.  Graf served for the championship at 5–3 in the third set, but lost the game at love and won only three more points in the match from that point.  It was the first of Sánchez Vicario's three French Open titles, which she also won in 1994 and 1998.

Supporting paragraphs: Steffi Graf Heinz Günthardt
Answer: "Steffi" Graf