When Peter Capaldi took over from Matt Smith in 2013, fans experienced a peculiar sensation of whiplash. The Twelfth Doctor was nothing like his predecessor as he was significantly older in appearance and had the temperament of a very grumpy man. No one was sure what to make of him at first.
Naturally, over the course of three seasons, the Twelfth Doctor mellowed and allowed his playful side to surface a lot more. He also developed a sweet friendship with Clara, and subsequently Bill and Nardole. However, this incarnation of the Doctor was still prone to acting selfishly, and without compassion.
He And Santa Harbored A Mutual Dislike
Santa Claus brings presents to households on Christmas Eve, and brings happiness to children on Christmas morning. If you can't get on with Father Christmas, then there's no real hope for you. Of course, the Twelfth Doctor was naturally very grumpy and he really didn't like cheerful people.
He could barely tolerate Robin Hood and his gang of Merry Men (who were, to be fair, extremely annoying) so it made sense that he didn't exactly get along with Saint Nick. However, the Doctor is a literal hero to so many people, therefore the fact that he got into a verbal sparring match with Santa was a bit depressing.
His Treatment Of Bill
Generally speaking, the Twelfth Doctor was a lot friendlier towards Bill than he was to both Clara and Nardole. He certainly didn't treat her nearly as poorly. However, the Doctor did still have his moments.
When he and Bill first met in an exciting adventure with magic space oil, the Doctor wanted to wipe Bill's mind without her permission. Not a great start admittedly. He then abandoned Bill to a horde of murderous robotic spacesuits without a glance (although he was blind at this stage) but his greatest travesty was when he broke his promise to protect her and subsequently, Bill got turned into a Cyberman.
Everything He Did As 'The Architect'
This took place early on in the Twelfth Doctor's run and demonstrated just how cold the Doctor really could be. He and Clara woke up in the Bank of Karabraxos with their memories wiped, along with two others. They were given a few supplied to help them infiltrate the bank, along with a spooky voice.
During the heist, their two extra companions chose death rather than having their brains turned into soup, all thanks to the callousness of the Architect. Near the end of the episode, however, it was revealed that the Architect was the Doctor, who had used time travel to break into the Bank.
His Dislike Of Danny Pink
In only the Twelfth Doctor's second outing, he made quite clear his dislike of soldiers. However, in the same episode, Clara met Danny Pink, a Maths teacher at her school who used to be a soldier. The two began to embark on an incredibly awkward but kind of sweet relationship.
Their relationship was progressing nicely until the Doctor arrived at Coal Hill School one day. It was then that he met Danny properly and it didn't go well. Thanks to Danny's past, and the Doctor's prejudice, the two loathed each other. The Doctor in particular thought that Danny wasn't good enough for Clara.
He Abandoned Young Davros
One of the more shocking moments in Doctor Who took place in Season 9's opening two-part serial. The premiere opened with a battle raging on on a distant planet. A young boy was alone on the battlefield, surrounded by Hand Mines. Luckily, the Doctor appeared to save him. But not for long.
After learning of the child's true identity, the Doctor left him to die so that the Daleks would never be created. It was eerily similar to the popular serial "Genesis Of The Daleks", in which the Doctor was forced to make an impossible choice. To abandon a child, though, is a whole new low.
He Refused To Regenerate
The Twelfth Doctor, for all his grumpiness, was quite a soft, sentimental character at the end. After a particularly devastating battle with the Cybermen and not one, but two Masters, the Doctor was left weary and injured, resigned to accepting his death and obstinately refusing to regenerate into another body.
This doesn't sound that bad when you put it on paper, and viewers watching the episode knew that he would change his mind at the end of his last adventure. However, if we accept that this was real, and that the Doctor might die once and for all, it would deprive us of Doctor Who forever.
He Shot The General
Season 9 really put the Doctor and Clara through the wringer, especially towards the end of the season. In the last three episodes, Clara died due to the machinations of Me, the Doctor was tortured for billions of years and finally, both the Doctor and Clara arrived on the former's long lost home planet.
At this point, the Doctor was in a very bad mood as he blamed the Time Lords for his best friend's death. However, he managed to extract Clara from the second before her death in an effort to save her. Unfortunately, the General stood in his way and so the Doctor shot him, causing him to regenerate.
He Let Spider Die
This was a surprisingly dark moment in an otherwise fairly light episode. In Season 10, the Doctor was travelling with Bill Potts, a young student who he had taken under his wing. In their third adventure together, the Doctor took Bill to the last Frost Fair on the River Thames.
However, it wasn't long before the Doctor had his sonic screwdriver stolen by a young child called Spider. The boy ran out onto the ice where alien fish circled him. Spider then fell through the ice but the Doctor seemed more concerned with rescuing his screwdriver than trying to save the boy, who was eaten.
His Treatment Of Clara
Firstly, Twelve and Clara had a delicious friendship for two whole seasons as they were both more than a match for each other. Unfortunately, during Season 8, the Doctor had an uncomfortable habit of belittling Clara every chance he got.
He commented negatively on her looks and appearance but that wasn't all. Soon after regenerating, the Doctor left Clara to the mercy of the Clockwork Droids, relying on her to get essential information. He also didn't like her boyfriend but the worst thing he did was leave Clara to make a huge decision and afterwards, patronized her by insisting he did it to help her.
He Let Ross The Soldier Die
This was quite frankly the Twelfth Doctor's most shocking and abhorrent moment throughout his run. Admittedly, the Doctor has never truly been at his best when confronting the Daleks but this was a new low. The Doctor and Clara, along with a bunch of soldiers had to enter a Dalek to try and find out why it suddenly turned good.
Along the way, they encountered Dalek Antibodies which exterminated intruders. The Antibodies had locked on to Ross, who asked the Doctor to save him. The Doctor promised, gave him a vial to drink and then the Antibodies killed him. The Doctor remained unfazed and uncaring, insisting that Ross was already dead.