Does every anime series have a bad ending?

[The Valkyrie]

Cowboy Bebop and Trigun (the anime) have good endings in my opinion.

Cowboy Bebop's ending is sad in some ways, but has warmth to it. Trigun is good because it gets to a point of such darkness and the viewer wonders how the main guy could ever fix things, but the ending is pretty warm and surprising.

 

[Azureknight 773]

Back to this thread, I can suggest .hack//Legend of the Twilight. It may have a cliffhanging ending because the "Mystery of the Key of the Twilight" hype has to be kept but the ending is cool as to all are united to fight together in their new adventure.