What anime (that you've watched) did you think had a perfect ending, and why?
had a perfectly emotional ending that shaped the main characters forever. Even having a time skip showing how all the characters are doing after the events that take place in the last episode.
had a perfect ending that Ryuk foreshadowed in the very beginning. Towards the ending, you can visually see Light losing is sanity ultimately resulting in his defeat. Lights short tempered mentality and his massive ego lead to his enevitable lose.
evil will always exist no matter what you do about it.
Death note was the best most well thought out ending of any story in any anime ever