Most disappointing follow-up?

Davies and Moffat both had an infuriating habit of introducing a plot thread within a decent or even great episode and concluding it with one so awful that it completely undermined the merits of its predecessor. I've included some of the most egregious examples in the poll; feel free to suggest others.

To me, the most disgraceful example of Moffat's craven cowardice and lack of professionalism has to be the insane decision to follow up Heaven Sent with a travesty like Hell Bent. It's almost as though he felt obliged to shit out an hour of spiteful anti-male virtue signalling to apologise for the crime of writing a thoughtful, imaginative story that allowed his leading man to shine with no ulterior political agenda.

Utopia had such a brilliant second half... well, until 'the Simm' appeared and gave a hint of the horrors to come. So it gets my vote.

I'm going to go with the Silence arc, esp since it started so well and then just fell away to nothing because Moffat suddenly decided to go against his "the audience aren't stupid" schtick and assume they were actually.

This is a difficult choice.

Last of the Time Lords was an awful follow-up (and of all the options, probably the one I hate the most) but I can't say I was surprised by RTD's worst writing anymore at this point. Therefore I can't say I was disappointed. Besides I've never really seen the point of continuing the Master beyond the 1970's.

Journey's End, possibly because of diminished expectations, didn't seem quite that bad even though there was a lot of holes in it. I guess partly because it had been such a vanilla season anyway.

End of Time was stupid but again by that point I was past caring anyway.

The Silence Arc was an almighty shocker to me because Moffat's era had started so well, but I can't say it was Time of the Doctor that was the point of disappointment. It was more like Let's Kill Hitler where my jaw dropped in horror. Time of the Doctor was just a bit mediocre with a few Matt Smith smile-raising moments. I didn't hate it.

Hell Bent, I'd already thrown in the towel by then. And I didn't even watch any of Series 10.

I'd probably go with 'other' as really A Good Man Goes To War > Let's Kill Hitler was my biggest WTF? moment.

I'll go with Oxygen through to Monk Trilogy, although I actually really liked Extremis, felt a bit ahead of the curb, DW does Black Mirror almost. The other two parts couldn't compete. It's not all Moffat's fault as he had a family tragedy at the time, but he should have trusted someone else to supervise it.