What's the worst Android UI / Manufacturer customization - Past or Present?

I owned a Nexus One in the past as I felt the only way to experience Android was with a pure version and none of this over the top stuff some of the other manufacturers. I am now eagerly awaiting the Nexus 4 so I can return to pure Android once again.

Reading these forums, I certainly hear mixed feelings to different manufacturer customizations. Some people love Sense whilst others sing nothing but praise for Samsung's TouchWiz, however for every person that says they love it; there is always someone who dislikes it.

So I ask you, Verge community - What is, or was the worst UI / Skin / Manufacturer customization in your opinion?

Blur? TouchWiz? Sense? Or even another lesser known or better left forgotten customization?

I look forward to hearing your responses.

Kev.