The main goal for Colin Baker's version of the Doctor was to come across as unstable, arrogant, and unpredictable. Both the Twin Dilemma and Attack of the Cybermen display these behavioural traits perfectly. The ending of the episode IS controversial for some people, but I think it was a necessary change. When a Time Lord regenerates, his whole personality changes. Anyone who has watched David Tennant knows the Doctor isn't above violence if it is necessary. And as always, watch the commentary because they discuss a lot of what went on behind the episode and why things were done they way they were. Great episode and wonderful to hear them talking about it years later.