The Tenth Doctor & Martha Jones
Martha Jones, despite her self-awareness, struggled to live up to the memory of Rose in the Tenth Doctor's eyes. Her unrequited love for the Doctor eventually led to her departure from the TARDIS, but she found her own happy ending.
Doctor Who's Martha Jones (Freema Agyeman) walks, followed by Ten (David Tennant) and Donna Noble (Catherine Tate)
The Eighth Doctor & Grace Holloway
The 1996 Doctor Who movie hinted at a romantic relationship between the Eighth Doctor and Grace Holloway, but it never materialized. Grace's rejection of the Doctor's invitation to join him on the TARDIS signified the end of their potential romance.
The Doctor and Grace Holloway kissing in the Doctor Who 1996 movie
The Eleventh Doctor & Amy Pond
The Eleventh Doctor and Amy Pond's brief flirtation was quickly overshadowed by Amy's marriage to Rory and the Doctor's marriage to River. The show's decision to backtrack on the romantic setup was for the better, considering the discomfort it brought.
Amy Pond kisses the Eleventh Doctor in the Doctor episode Flesh and Stone
The Thirteenth Doctor & Yaz Khan
The implied feelings between the Thirteenth Doctor and Yaz were left unresolved, despite multiple hints throughout their time together. The lack of proper addressal of their potential romance ultimately left fans disappointed.
Yaz hugs the Thirteenth Doctor in Doctor Who
The Eleventh Doctor & Clara Oswald
Clara's flirtatious behavior with the Eleventh Doctor often went unacknowledged, leading to an uncomfortable dynamic. The shift in Clara's relationship with the Twelfth Doctor signified the end of their romantic undertones.
The Eleventh Doctor (Matt Smith) puts his arm around Clara (Jenna Coleman) in the Doctor Who episode Hide
The Tenth Doctor/John Smith & Joan Redfern
The Tenth Doctor's human love life with Joan Redfern was short-lived, as she rejected his invitation to join him on the TARDIS. Despite the setup, their bond came to an abrupt end, leaving the Doctor to carry on with his adventures.
The Tenth Doctor as John Smith kissing Joan Redfern in his study