(Photo: BBC America) 
Not every TARDIS traveler has a traumatic final farewell with the Doctor, but a good many do. And with Ace, Tegan AND Donna Noble making their returns to our screens at some point in the imminent future, it’s worth taking a look at which of the Doctor’s friends made it out with their dignity, minds and hearts intact, and which… didn’t.
But before we get started, here’s a quick summary of all of the (TV only) companions who have managed to leave active service with the Doctor without undue sacrifice or tragedy, and a brief summary of what happened:
Barbara Wright and Ian Chesterton (left as soon as the Doctor got them to London in 1965, two years after they first came on board)
Vicki (stayed with the Greek warrior Troilus, became the actual Cressida)
Steven Taylor (elected to remain on an unnamed planet in order to ensure peace between warring tribes)
Dodo Chaplet (retired to the country)
Ben and Polly (left the TARDIS on the same day they arrived)
Victoria Waterfield (found a nice family to stay with)
Liz Shaw (got tired of handing the Doctor test tubes)
Jo Grant (met her future husband)
Sarah Jane Smith (dropped off in South Croydon, possibly)
Harry Sullivan (took the train home)
Leela (married a Time Lord)
Romana (went off to explore E-Space)
Nyssa (set up a hospital on a space station)
Vislor Turlough (returned to his home planet)
Peri Brown (married King Yrcanos of Thoros Alpha)
Mel Bush (left to travel with a confidence trickster)
Ace (set up an international charity)
Grace Holloway (didn’t want to travel)
Mickey Smith (became a fighter)
Nardole (kicked Cyberman ass)
Graham O’Brien (settled down to life as a former bus driver)
Ryan Sinclair (never quite mastered riding a bike)
And here’s the definitive list of final farewells in ascending order of heartbreak, starting with the first:
14. Susan Foreman – “The Dalek Invasion of Earth”

The trope of the young female companion finding love and leaving the Doctor behind was to become a relatively common one in classic Who, but Susan is the only companion to be forcefully abandoned as soon as she gets her first boyfriend. And she was the Doctor’s granddaughter! Oh, sure, she gets a fine speech from the old man, but still… families, eh?
13. Adam Mitchell – “The Long Game”

Granted, this is not so much heartbreaking as it is sobering. If you travel with the Doctor and you fail to demonstrate the right kind of moral code, you will earn his displeasure. His displeasure is not nice. Adam downloaded the future into his own brain, and was kicked out of the TARDIS as a result. This shows the same steely side of the Doctor that Susan faced, only with a righteous zeal because, well, Adam deserved it.
12. Jamie McCrimmon and Zoe Heriot – “The War Games”

We will return to the subject of wiped memories later on, but in this tale, the final goodbye of loyal Jamie McCrimmon and his space-ace pal Zoe involves having their time with the Second Doctor forcibly removed from their synapses. They seem remarkably unaffected by this invasive procedure, and are even shown resuming their former lives with remarkable ease, but there’s something about the famously non-intrusive Time Lords playing about with people’s brains that leaves an unpleasant aftertaste.
11. Clara Oswald – “Face the Raven”

When is a death not a death (part 1)? Clara takes on the blood debt owed by Rigsy, in the form of a countdown tattoo, assuming she’ll be able to cheat it. It turns out she can’t, and her hubris ensures that she has to pay the ultimate price – death by raven - and she dies. But just before she goes, the Doctor borrows her from her own timestream, and then by the end of “Hell Bent” he sends her on her way, to have a ton of adventures in her own TARDIS with the functionally immortal being Me. If it’s possible to be heartbroken and then have your heart unbroken while being told the heartbreak still stands on a technicality, this is that.
10. Tegan Jovanka – “Resurrection of the Daleks”

This clip says everything about the gulf between what the audience experiences of the Doctor’s adventures and what the characters have to experience. “It’s stopped being fun,” says Tegan, having witnessed yet another alien atrocity, this time at the suckered hands of the Doctor’s most fearsome enemies. The unspoken assumption being that, possession by an enormous snake (“Kinda”) or having your aunt killed by the Master (“Logopolis”) will have been much more entertaining. But really, Tegan’s word are a stern rebuke to the seemingly unflappable glee with which the Doctor embarks on his adventures, and therefore a moment of reality for us too.
9. Martha Jones – “The Last Time Lord”

On a similar note, the events leading up to Martha’s final farewell are among the most transformative any companion has had to experience. She’s become a super-soldier, and a missionary. She roams the Earth, reaching out to communities devastated by the Toclafane killing spree – instigated by the Master – and encouraging them to believe in the Doctor. On his command, she channels and exploits her own romantic feelings in order to convince humanity to put their faith in him. And when it works, she saves the world, but the entire experience is erased from history. Only her family know. She may say they need her support to recover, but she surely needs theirs just as much.
8. River Song – “The Husbands of River Song”

When is a death not a death (part 2)? The heartbreak has already happened by the time we get to see this scene. Due to the topsy-turvy nature of River Song ad the Doctor’s respective timelines, we already know she’s destined to visit a library-ful of Vashta Nerada as soon as she leaves the Singing Towers of Darillium, and there she will meet her untimely end (sort of). So this is a last goodbye from the Doctor she knows and who knows her. Desperately sad, unless you know how long the goodbye is going to take.
7. Amy Pond and Rory Williams – “The Angels Take Manhattan”

At the other end of the scale, here’s a goodbye which takes place unexpectedly, at the end of an adventure, and with a devastating affect on the Eleventh Doctor. Having driven the Weeping Angels out of New York, Rory chances upon his own tombstone. Then he’s pinged back into the past by a last rogue Angel. The TARDIS can’t go after him, so Amy takes the plunge herself, thereby robbing the Doctor of his in-laws, and Rory’s dad of his own son. Although resolutely un-fatal, this goodbye is both brutal and hugely affecting. Just like…
6. Rose Tyler – “Doomsday”

The first major heartbreak of the modern era of Doctor Who. The big split between Rose and the Doctor was foisted upon them by circumstance. Rose was being dragged into the void with all the Daleks and Cybermen, lost her grip, and was only saved from certain death by her dad, who transported her back to the alternative dimension in which he is alive. The Doctor can’t follow, and her travels seem to be over. She does eventually make it back, and is even given her own metacrisis Doctor to play with, but this original farewell is anything but fond.
5. Katarina – “The Daleks’ Master Plan”

The first companion to die in Doctor Who, Katarina was an ancient Trojan serving girl who was taken from her time and homeland by the First Doctor and plonked straight into a Dalek conflict, in which she died. Her character had been conceived as a permanent occupant of the TARDIS but the reality of writing for someone who didn’t even know what a key was forced the show’s producer’s to cut her tenure short. So short, in fact, that the very first scene Adrienne Hill filmed as Katarina was her death scene. Maybe the Time Lords had a point about meddling in intertemporal affairs after all.
4. Adric – “Earthshock”

Actual death trumps all other forms of heartbreak in almost all cases. Adric’s demise, while accidental and probably entirely avoidable, is a rare example of classic Doctor Who killing off a companion and then making no effort to make it OK for the show’s younger audience. Adric, a math genius, was about to leave a crashing spaceship, but in a fit of youthful arrogance, hops back to the control deck to try and solve a complex equation. He then dies when a Cyberman shoots the console before he can put his answer in, and the spaceship crash lands into prehistoric Earth, probably killing off the dinosaurs in the process. Nice work, Brainiac.
3. Donna Noble – “Journey’s End”  

When is a death not a death (part 3)? Make no mistake; when Donna Noble has her memory destroyed by the Tenth Doctor – in order to contain those parts of her that have taken on Time Lord intelligence and prevent her mind from burning up – she dies. The person she becomes in the presence of the Doctor no longer exists, and an alternate reality Donna Noble, who never saved the universe, returns to her everyday reality with no knowledge of the luminescent person she had become. What’s worse is that she knows this before he does it. And what’s worse than THAT, is that he’s the one who has to do it, and it’s his metacrisis intelligence that has put her at risk. He made her, he kills her. The end.
2. Bill Potts – “The Doctor Falls”

When is a death not a death (part 4)? In reality, Bill Potts dies pretty early on in the events depicted during “World Enough and Time”, but somehow she is resurrected with machine parts, thanks to a Dickensian scientist (who is the Master). By the time the Doctor can get to her, however, she has died so many times her body has been entirely replaced, and all she can say, to express this endless horror from inside her Mondasian Cyberman frame is “I waited”.  This is a heartbreak played out as eternal torture, on a par with Old Amy in “The Girl Who Waited,” and one that only really ends in both cases with the blessed release of death. This is really chilling stuff for a family TV show. Bill may get a second lease of life when rescued by Heather and transformed into a space and time traveler, but does that take away the memory of those tormented years? Nope.
And the most traumatic exit of all time is…
1. Kamelion – “Planet of Fire”
OK, so this isn’t often talked about, but did you know that the Fifth Doctor had a shape-shifting robot companion called Kamelion who got mind controlled by the Master and was controlling the TARDIS navigation systems? And do you know what the Doctor did to fix that situation? He blew Kamelion up, then used the Master’s tissue compression doodad to shrink him down to tiny size, thereby killing him. And this was after Kamelion BEGGED him to do it. And there was no Bill Potts afterlife for this (literal) cyber man. This death is permanent.
Do you become attached to each companion, before... you-know-what?