The anime ending is embarassing (spoilers, obviously)
Almost immediately after the battle in the giant vortex thing, the show went downhill to a ridiculous degree. The giant robot battle a few episodes from the end is embarrassing, and the battle of Death vs Asura was pretty cheesy too. I'm so disappointed, because until the anime stopped following the manga, it was really good.
I haven't read the manga yet, but I really hope the ending is better. Though honestly, it'd be hard for it to be worse.