diagonal: Thanks, <Honza Cervenka> for honoring Nana Alexandria, twice Women's World Championship Challenger, against Gaprindashvili in 1975 (lost), and against Chiburdanidze in 1981 (drew).
Despite not winning the ultimate title match, the following World Champions could retain their title without a tie-break:
Lasker in 1910: Drawing with Schlechter 5-5
Botvinnik in 1951: Drawing with Bronstein 12-12
Botvinnik in 1954: Drawing with Smyslov 12-12
Chiburdanidze in 1981: Drawing with <Alexandria> 12-12
Kasparov in 1987: Drawing with Karpov 12-12
Kramnik in 2004 (split title): Drawing with Leko 7-7
In these matches, the reigning World Chess Champion kept the title without any further play-off, according to the rules then in charge.
Schlechter, Bronstein, Alexandria, and Leko never became World Champion.
Note: Botvinnik played five regular World Championship title matches (1951, 1954, 1957, 1960, 1963), he didnt win one! Botvinnik drew Bronstein (1951), drew Smyslov (1954), lost to Smyslov (1957), lost to Tal (1960), lost to Petrosian (1963). Two re-matches (a special regulation then in charge), he did win, vs. Smyslov (1958) and vs. Tal (1961). The re-match clause had been abandoned in 1963, later re-installed for Karpov, finally buried.