Fullmetal Alchemist: Brotherhood
Great premise, solid foundation, but ruined by breaking built immersion, mood, and significant with low-fidelity-styled bad jokes.
I loved the predecessor; the original Fullmetal Alchemist series 2004. When I watched it in 2005 I rated it 10/10.
When I first started watching Brotherhood in 2009, I loved the refreshed great visuals, and hated the unnecessary, ruining jokes. They made me stop watching.
I recently sat through it though. The ruining gets a bit more scarce later on in the series, but still there. The impression I had back then remains.
Watching it made me want to rewatch the original from 2004.
Otherwise, the it is a great series through and through. Really unfortunate.