The problem with The Sixth Doctor:
22 March 1984 - 6 December 1986.
The characterisation for this Doctor was unlike any other the most deliberately dislikable and acerbic from his very first story, designed to gradually become more likeable and more mellow as time went by.
However, though in certain stories, Six was much less dislikable and more settled, his overall dynamic with his companion, Peri was alarmingly something like a real-life abusive relationship, his constant verbal abuse and mood outbursts being quite uncomfortable for viewers.
Six would grow less unlikable and more approachable over the course of his initial season and into his second, however stories like Mindwarp would reset him temporarily to The Twin Dilemma-esque proportions of sheer toxicity.
Overall, stories which helped his cause the most in terms of his character were Vengeance on Varos, The Mark of the Rani, The Mysterious Planet and Terror of the Vervoids. Despite being quite workable on story levels, The Two Doctors and Revelation of the Daleks still included ounces of the more reprehensible and nastier Six, cruelly and invalidly attacking Peri's weight for instance.
Ultimately, the idea to create a Doctor so thoroughly hateful and with such a loud, obnoxious costume matched with a nihilistic, cynical Doctor Who that was all about death, grittiness, gore and destruction more so than actually wanting us to be attached to its hero has been proven an absolute disaster.
It's no small wonder the reason Big Finish has been so successful with this Doctor is that it removed all the things which destroyed him on television, specifically the barbs to his personality and his terrible companion dynamics.
